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Amazon best sellers

Analyze review tools



Build PC

cpu thermal paste

How to Re-Paste Your CPU With Fresh Thermal Paste

Computer motherboards form factor comparison

Mini ITX

PC stick

Possible cons:

  1. No Ethernet port
  2. Can get very HOT
  3. No Audio out jack
  4. Does not use opensource chipsets for wifi/bluetooth.



Renewed i5 Mini PC: HP EliteDesk 800 G2, Amazon. i5 6500T 2.5Ghz. ebay (half price).

Intel NUC

ODroid-H2 (Intel Celeron J4105 Gemini Lake processor, 2018) $111

UDOO x86 PENTIUM N3710 (ultra), CELERON N3160 (advanced) 2016.

mini pc + external GPU


MINIX NEO Z83-4U Fanless, Ubuntu 18.04, $180.

Asus mini PC

Asus PN50 mini PC with Ryzen 7 4700U now available in the US

Single board computer

Rock Pi x


What Is a “Chipset”, and Why Should I Care?

Intel Processor

G, H, K, T, Y, U, Y Processor Suffixes

CPU socket

CPU Socket Types Explained: Socket 5 to BGA

Intel & AMD CPUs

Explaining Intel & AMD CPUs (video)



What Is Hyperthreading?

Thunderbolt docks

Best Thunderbolt docks 2023: Extend your laptop’s capabilities


  • The best 4K monitors for desktops 12/2022
  • Time to upgrade your monitor. If you’re shopping around for a new monitor, and you have to choose between higher pixel count or a high refresh rate, you should 100% without a doubt go for the higher refresh rate. The difference 120Hz or 144Hz will make in just how smooth and responsive a UI can be is astonishing. I think the sweet spot is 1440p at 144Hz, preferably with FreeSync or Gsync.
  • iNNOCN 2watt was used when I connected it to ubuntu as a second monitor.

HDR/High dynamic range

What Is DisplayHDR?

USB-C Pass-through charging

The New Xpanel 4 Portable Monitor: The Best Steam Deck Accessory You Can Get!

USB-C alt mode


MSI Afterburner

Core Temp

  • How to measure cpu power consumption

stats for nerd in Youtube


What Is VRAM?


My own collection of SoC

Device Family Instruction Clock & Memory
Pogoplug ARM9 ARMv5 1.2GHz, 256MB
Raspberry Pi ARM11 ARMv6 700MHz, 512MB
Beaglebone Black Cortex A8 ARMv7 1GHz, 512MB
UDOO Cortex A9 ARMv7 1GHz, 1GB
Odroid Xu4 A15 & A7 ARMv7 2GHz & 1.4GHz, 2GB

See wikipedia for a list of ARM cores. These SoC are 32-bit. The newest ARM architecture is ARMv8 which is 64-bit; see here.

Comparison of single board computers from Wikipedia

Arduino Yun vs BBB vs Intel Galileo vs Raspberry Pi

from Adafruit. It includes spec comparison, performance test, power usage, ...

Low-to-medium range PC/tablet and Chromebox


Lenovo IdeaTab Lynx K3011

Intel® Atom™ Z2760, 2G ram, 64GB storage and Micro-HDMI.

Lenovo chromebook S330

Feel fast especially on Terminal.

Dell Inspiron 2-in-1 14" Touch-Screen Chromebook

Bestbuy $399. Full HD, 4GB memory, 128GB eMMC. Stylus. Intel Core i3 CPU.

HP Chromebox Desktop, CB1-101

Intel Celeron 2955U Processor 1.4 GHz, 2GB DDR3 RAM, 16GB ssd, Year 2014

It is not updated for the meltdown & spectre bug. See this list.

To enter the developer mode, use the 'reset' button (a small hole next to Kensington lock). See

To invoke developer/recovery mode, you insert a paper clip and press the RESET BUTTON (just beside the kensington lock) and press the Power button. Release the RESET BUTTON after a second.

To enter Dev-mode you first invoke Recovery, and at the Recovery screen press Ctrl-D (there's no prompt - you have to know to do it). It will ask you to confirm by pressing the reset BUTTON again.

Dev-mode works the same as always: It will show the scary boot screen and you need to press Ctrl-D or wait 30 seconds to continue booting.

It seems the 'Reset' button is called 'Recovery' button on ASUS chromebox. See here.

See Gallium OS.


ASUS Chromebox CN60 (M075U)

ASUS website. 1.7 GHz Intel Core i3-4010U Processor, 4GB of 1600 MHz DDR3 RAM, 16GB Solid State Drive, Year 2014

A newer one is CN62.

Both are not updated for the meltdown & spectre bug. See this list.

ASUS chromebook C423

https://www.amazon.com/Chromebook-C423NA-DH02-NanoEdge-display-Processor/dp/B07HRZM2V4/ $269

HP Stream 8

Intel® Atom™ Z3735G Quad Core (64-bit), 1G ram, 32GB storage. The C: drive shows the space is 23.5 GB. The free space is 20GB. After the first Windows update the storage space is reduced from 18.6 to 16.8. After running Disk cleanup utility, the storage now becomes 17.1 (still lose a lot). So the lesson is not to run Windows update if the disk space is very limited (eg tablet) & everything is working fine now.

Low cost laptop

Best Chromebooks That Run Android Apps


Laptop weights

  • Macbook Pro 2015- 4lb 6.9oz
  • Lenovo Thinkpad T420s - 4lb 1.0oz, removing DVD - 3lb 12.7oz
  • Lenovo Thinkpad T440s - 3lb, 7.4oz. Touchpad design makes cursor jumps when clicking.
  • Lenovo Thinkpad E480- 3.85lb
  • Lenovo Thinkpad X1 carbon (6th gen)- 2.49lbs
  • Lenovo Thinkpad 13 Chromebook (usb-c) - 3.2lbs
  • Lenovo ThinkPad L390 - 3.2lbs (L-series for business customers)
  • Lenovo Flex 14 81SS0005US - 3.52lbs

Best Laptops

Clean laptop screen

How to Clean a Laptop Screen Without Damaging It


Take Your Projector On The Go With These Accessories

Samsung pico DLP projector sp-h03

LED, 30 ANSI lumen 854x480, 12V & 1A power. The manual is available at Samsung web site here. The input signal in D-Sub can be 1280x800, 1280x768, 1280x720 resolution although the manual also said "All resolutions higher or lower than 854 x 480 are converted to 854 x 480 by the scaler chip in the projector. To obtain an optimal picture, the resolution from the PC should be similar to the projector (854 x 480)".

Vivitek Qumi Q5

500 Lumen WXGA HD 720p 3D-Ready Pocket DLP, 19V/3.42A/65W (buydig.com, ebay, vivitekusa.com, Manual)


amazon. Fan is noisy! 1080p video downloaded from youtube can't be played (720p is OK). Power consumption is about 114 Watt. No dedicated button for volume control when playing music. No zoom-in option for viewing text. No build-in Android OS. When connected to Jetson nano, the font looks tiny:(






Hard disk

Signs Your Hard Drive Is Failing

3 Signs Your Hard Drive Is Failing (And What to Do)

Hard drive comparison

The Most Reliable Hard Drive Models

Backup media

Hard-core data preservation: The best media and methods for archiving your data

Hard drive docking station

Remove magnets




  • How to Estimate the Remaining Lifespan of Your SSD. On average, a modern SSD will survive until you've written about 700TB of data over its lifetime (Total Host Writes). Software: CrystalDiskInfo.
  • Linux. Smartmontools NVMe support
    $ sudo apt install smartmontools
    $ sudo smartctl -A /dev/sda         # 2.5" SSD
      1 Raw_Read_Error_Rate     0x000b   100   100   050    Pre-fail  Always       -       0
    241 Lifetime_Writes_GiB     0x0012   100   100   000    Old_age   Always       -       7829
    $ sudo smartctl -x /dev/nvme0n1p2   # NVMe SSD
    Data Units Read:                    1,808,590 [925 GB]
    Data Units Written:                 432,671,903 [221 TB]

2.5 inch SATA SSD and M.2 SSD



SATA 採用 B + M Key 的設計,而 PCIe 則為 M Key 設計,兩者並無法相容。




Your Next SSD Might Be Slower (Thanks to QLC Flash). In short, QLC SSDs Break Down Much Quicker. You should definitely avoid QLC drives with 512 GB and less. QLC flash isn’t too much of an issue when you look at the higher capacity drives.

Portable SSD

Trim and defrag

更新 Windows 10 後竟會降低 SSD 使用壽命!微軟表示:想辦法修復中, Microsoft is preparing a fix for a Windows 10 bug that affects SSDs


MicroSD card

Micro SD Card Ratings Definition Reference

Health monitor

Maximize the lifetime

  • Some helpful tips on extending the life of your card
  • The MicroSD card should be reformatted every 2 weeks to maximize the lifetime of the memory card (from the manual of Vantrue N1 Pro Mini Dash Cam) .
  • How often should memory cards be formatted?
    • Formatting clears the directory structure of the card and removes any artifacts that might be left behind by erasing. Repeatedly using the ERASE and ERASE ALL camera options and not formatting can result in a buildup of file artifacts that may eventually cause the card to fail.
  • How often does a microSD card needs to be formatted?
    • While the quick format will simply clear the filesystem table so all the space on SD card will appear as available (the data is still on the card), the full format will also check for errors and remove all the data from the card by writing zeros (for example).
    • Formatting is a more complete way of clearing old files from your card and can reduce the risk of data corruption.
  • How and Why Should I Reformat My Memory Card?
    • Deleting or erasing a file doesn’t necessarily remove it. Instead, your card will simply write over the “deleted” files whenever you save new data. This means the “deleted” files remain on the card until they’ve been replaced. Reformatting is a more thorough security measure that ensures you permanently erase all the data before adding new files or images. It’s the only way to rest assured that a file is truly erased.

Speed comparison

Best microSD cards

Why your laptop's SD card reader might be terrible

Why your laptop's SD card reader might be terrible

USB device speed comparison

See http://www.elinux.org/RPi_SD_cards#Performance for an objective way to get write/read speed by using command line tool 'dd'.

Device Read Write FS
MicroCenter4G Example 12.77MB/s Ext3
MicroCenter4G Example 5MB/s vfat
Patriot XT 32G USB3.0 Example 50MB/s vfat
Patriot XT 32G USB3.0 Example 115MB/s fat16
Patriot XT 32G USB3.0 Example 113MB/s fat32
Patriot XT 32G USB3.0 Example 24MB/s ntfs
Patriot XT 32G USB3.0 Example 139MB/s ext2
Patriot XT 32G USB3.0 Example 50~100MB/s ext3
Patriot XT 32G USB3.0 Example 140MB/s ext4
Example Example Example vfat

When testing Patriot XT USB 3.0 drive, I partition it into ext2 (15GB)& ext3(15GB). The problem of unstability in Patriot XT's ext3 partition is not related to ext3 partition because if I switch the order of partitions of ext2 and ext3, then ext2 becomes unstable.

  • A word about USB flash drive.
    • According to the Slo Bytes USB Flash Drives report from Brian K. Lewis, flash drives are capable of handling 10 thousand to 10 million write and erase operations during their lifetime, depending on the source as well as the specific USB drive. Regardless, a flash drive typically will outlast any standard hard drive. The main concerns about the life expectancy of a flash drive are damage from neglect and becoming lost or stolen.
    • The life expectancy of a USB Flash Drive can be measured by the number of write or erase cycles. USB flash drives can withstand between 10,000 to 100,000 write/erase cycles, depending on the memory technology used. When the limit is reached, some portion of the memory may not function properly, leading to lost of data and corruption.
    • Most experts would agree that around 10 years is about what you can expect to retain data on a flash drive without powering it up. That means you can lock away a USB drive for 10 years and return to still see your data. After 10 years of not being powered on, the electrical charges determining if bit of information is either a ‘1’ or a ‘0’ gets hazy. This is because like all electrically charged devices, they suffer from what is called electro/magnetic deterioration; or simply put, where devices will eventually lose their power.
  • The copy-paste speed on my 7200rpm hard disk is about 160MB/s.
  • Tested using Seagate portable drive SRD0SP0 500GB with USM((Universal Storage Module)/USB 3.0. When it is connected to USB 2.0/3.0, the writing (from an internal hd onto it) speed is at best 30MB/s. When it is connected to USB 3.0, the writing (from it to an internal hd) speed is at least 60MB/s.
  • DIY USB on the go cables.

M2 NVMe to USB enclosure



ATX 24pin power supply

and this. A simple test from wikihow.com.

Blu-ray Drive

Nintendo Devices hack

5 Ways to DIY Hack Your Old Nintendo Devices Into Something New

Cellular phone

Cellular phone frequency list

In particular, T-mobile (T-mobile Band specs and Radio frequency spectrum chart from Wikipedia) uses

  • 1700 (3G UMTS),
  • 1900 (3.5G HSPA+),
  • 2/4/12 (4G LTE)

Chunghwa telecom uses 2100 for 3G/3.5G.

What is the difference between G, E, 3G, H, H+ and 4G symbols? We find out!. The order is (from fastest to slowest)

  1. 4G
  2. H+
  3. H
  4. 3G
  5. E
  6. G
  7. 2G

Verizon, AT&T, T-Mobile, and Sprint: Which Mobile Carrier Is Best for You?




Mobile virtual network operator

3 Ways to Find Free Unlocking Codes for Mobile Phones


How to Block Unknown Callers


When to get a new cell phone

12 Warning Signs It’s Time for a New Cell Phone

Buy a phone

Phone plan

trackfone $20 a year

FLIRC FL-09028 USB Universal Remote Control Receiver

Remap any Controller to Keyboard Keys

How to Remap any Controller to Keyboard Keys on Windows, Linux and MacOS

Vehicle camera recorder

1. night vision 2. can turn on/off manually 3. pictures stable (not flicker) 4. G-sensor 5. 3D turning on mount racket 6. no surprising things like auto turned off, (power, start) buttons not working, freeze 7. video space (640x480 takes 100MB for 1 min???). The Amazon website has a list of popular dash cams.

Security Camera

Mirrorless & DSLR cameras

Mirrorless Camera

Nikon D5600 camera

Can anything be done to reduce the shutter sound on my SLR?



Lens Hood

What Does a Lens Hood Do, and When Should You Use One?

Wide angle lens

What is a wide angle lens

Sensor and Pixels

The Pros and Cons of Larger Smartphone Camera Sensors

Photos tips

Image editing

How to Use Darktable, the Free Adobe Lightroom Alternative


DPI vs. PPI: What Is the Difference?

Wifi SD card

Add Wi-Fi to Your Mirrorless/DSLR Camera


CEC (Consumer Electronics Control) allows for control of devices over the HDMI port.

HDMI splitter

How to Split an HDMI Signal to Multiple Displays (And 3 High-Quality HDMI Splitters)

micro HDMI vs mini HDMI


  • Mini HDMI/Type C (flat, wider) is used on DSLR cameras standard sized tablets. Raspberry Pi zero. 7.8in Not-eReader. Anbernic rg353V.
  • Micro HDMI/Type D (small like micro-USB) is used on smaller portable devices such as smartphones and smaller tablets. Raspberry Pi 4. Retro Pocket 2. Beaglebone black.


Apple TV

Beginner's guide: How to get started with your new Apple TV

Google Chromecast

Amazon Echo


Google Home

How to Use Your Google Home as a Bluetooth Speaker

Amazon Fire TV

Install Kodi

Bypass Google’s YouTube block on the Amazon Fire TV


Change settings for privacy

Roku, Apple TV, Fire TV and Chromecast settings to change to protect your privacy

Amazon Kindle ebook reader

Send to kindle web extraction failed when I tested 'Send to Kindle' from an iPad.

But it works when I use the Chrome extension on the Chrome browser.

Kindle Paperwhite 安裝英中字典

To take screenshots, just hold down on on the top left and button right, or the top right and bottom left. The pictures are stored in the root folder of your Kindle Paperwhite. You can plug your e-reader into your PC via the USB cable and get access to any of the pictures you took.

To use Kindle to read news, use Calibre or reabble.com (based on https://www.inoreader.com).

12 Sites Every Kindle Owner Should Really Know About

Identify Kindle generation

How to Tell Which Kindle I have? --Identify Kindle Model Updated Dec 2019

https://www.amazonforum.com/help/identify-your-kindle-e-reader. Mine is paperwhite 7th generation released 2015.

It is also called 'paperwhite 3' (4 LED frontlight) according to this

Kindle Paperwhite 3 (2015, 7th generation) vs Paperwhite 2. Both have built-in front light. Paperwhite 3 has 300 DPI while paperwhite 2 has 216 DPI.

Paperwhite (10th generation, 300 ppi, released November 2018) has bluetooth. Can't Connect to Bluetooth

Power saver mode

Power Saver Mode on Kindle Paperwhite, Have You Tried Disabling It?

Send to Kindle

The following file types are supported for Send to Kindle: - Microsoft Word (.DOC, .DOCX) - PDF (.PDF) - Text (.TXT) - Images (.JPG, .JPEG, .GIF, .PNG, .BMP) - Kindle Format (.AZW, .MOBI) - Other File Types (.RTF, .PRC, .PSZ)

  • Browser (send web content): Chrome and Firefox (Not compatible with Firefox Quantum)
  • PC or Mac (send documentations)
  • Email (send documentations)
  • Android (send documentations)

Question: how to do it in R?

How to Send Articles to Your Kindle for Later Reading with Tinderizer, Instapaper, or Pocket

New Push to Kindle Android app from fivefilters.org. We no longer require email addresses to be entered to send articles.


Using Pocket on Kindle Devices

Kinstant - the start page for Kindle's web browser


Removing Kindle User's Guide

https://www.mobileread.com/forums/showthread.php?t=288690. Change the selector at the top left of the library screen from "ALL" to "DOWNLOADED". The "ALL" option shows you all the items in your Cloud library; "DOWNLOADED" shows you just what's currently on the device.





Amazon Kindle Fire Tablet




Smash Mute.The Big, Fat TV Mute Button

Cordless Phone

Panasonic Troubleshooting - Error Message "No Link to base" Menu - Initial setting - Registration. Follow the screen to press the 'Locator' on the base for 5 seconds and then press 'OK' on the handset. Done. ✅ See also p35 on the manual for registering a handset.


Best headphones: Our top picks for personal listening. Over-the-ear headphones explained, Wireless headphones explained, Noise-cancelling technologies explained.

What Are Decibels (dB)

What Are Decibels (dB)?

Multipoint in bluetooth

Some examples





Gallium nitride (GaN) charger

What Is a GaN Charger, and Why Will You Want One?

Portable battery

USB-c Power Delivery

PD usb-c battery

Search: Best USB-C Power Banks : Best Power Delivery (PD) Portable Chargers

How long will it power my device

working time = (Wh from the power station)* 0.85/ (watt of your device).

USB Hand Warmers

Are USB Hand Warmers Safe? Ocoopa Give You Answer

You Really Can Charge Your Phone With a 9 Volt Battery

From Lifehacker. A car charger is required. Line up your 9 volt battery, with the big (negative) battery terminal on the spring, and the positive (smaller) terminal touching the button in the center of the car charger.

How to test a solar panel using multimeter

`How to test a solar panel, How To Test Your Solar Panel - Quick And Easy INNOVA

  • Back of the solar panel should have a label to show the specification/numbers. Pay attention to Voltage at Pmax and Short Circuit Current.
  • Plug the red probe to V/omega/mA (red) and turn to DCV (red) to check the voltage. The reading number should be close to the label.
  • Plug the red probe to DC10A (yellow) and turn to DC10A (yellow) to check the amps. There will be a spark when we connect them. Cloudy day will affect the amps.

Portable power station

  • 5 Things You Should Look for When Buying a Portable Power Station
  • Modified vs. Pure Sine Wave Inverter: What’s the Difference?
  • You can use it as a pass through UPC backup if the power station supports the pass through.
  • If we try to provide more than 1 input (eg solar & 120v AC & 12V car charger at the same time), then only 1 input will be taken. There is a maximum charge rate. But it seems it does not hurt if we supply more than 1 input at the same time.
    • Golabs R300 has a Solar Panel (62w input max), Wall Outlet (42w input max), Car outlet (42w input max), or Generator (42w input max). Charging ways. GOLABS portable power station is built in an MPPT controller, the voltage is 10.8-23.5V (3A), the maximum input power can reach 60W. Car charger adapter is included (Car cigarette to power station input port). The cigarette socket on the power station is for output (12V/10A); e.g. tire inflator.
    • Golabs R150: similar to R300 except the capacity.
    • When I connect it to a solar panel it starts beeping and shows E09. What does that mean? It means over volt on the input power source. Just ignore the E09 error. According to the manual E09 indicates COVP (circuit over voltage protection). The solar panel output voltage should not exceed 22 Volts.
    • E08 error code on Anbernic rg353v. It cannot turn on nor charging.
  • The full charging cycles is about 500-200 before it drops to 80% on subsequent charges.
  • Charge it every 3-6 months.
  • Many has a built-in MPPT controller (means faster charging with a solar panel).
  • Not store it in a below 0C temperature environment.
  • Check the Watt requirement of a electronic device if we want to power it with the portable power station.
  • GOLABS Portable Power Station, 299Wh LiFePO4. It includes a PD USB-C port. It allows to use AC while it was charged. DC connection is 5.5x2.1mm. 12V DC output is not regulated.
    • GOLABS Portable Power Station, 204Wh(=63750mAh * 3.2V), R150 PD 60W USB C. One thing to note when charging via 2.1 mm plug you will not be able to use the USB power delivery port. Because this is a modified sine wave (inverter) some (AC) electronics may produce extra noise. I guess if I just use its USB-C connector (DC not AC), it would be OK (at least the power station's fan is not making any noise).
    • Can a Modified Sine Wave Inverter Damage Electronics? Suffice it to say that if it doesn’t use an AC motor, isn’t a delicate piece of medical equipment, and doesn't fit into any of the other no-go scenarios, you’re probably going to be in the clear. .... your laptop is probably going to be fine. If the device you want to power up runs on DC power in the first place, like a laptop, you're actually better off looking for a way to skip the transition from DC to AC and back to DC.
  • Jackery Portable Power Station Explorer 240. It allows to use AC while it was charged. DC connection is 8mm.
  • ROCKPALS 300W Portable Power Station, 280wh (78000mAh) Solar Generator. Connection 5.5x2.1mm. Con: AC port cannot be used while charging. Only the DC ports (USB, 12V) can.
  • Anker Powerhouse 200, 213Wh/57600mAh Portable Rechargeable Generator. 57600mAh * 3.7V/1000 = 213Wh.

Portable battery != Jump starter

Solar panels

Connect Any Solar Panel To A Portable Power Station

Solar Charge Controller, Battery


USB voltage meter

Kill A Watt P3

Note: click the 3rd button to switch between Watt and VA; similarly for the 4th and 5th button.

Volt --- Amp --- Watt/VA --- Hz/PF --- kWH/Hour

The relation of Volt-Amp-Watt-VA-PF are

1. VA = Volts x Amps
2. Watt =  VA x Power factor  (OR W = VA x PF)

For example, if the apparent power is 3000 VA and the power factor is 0.8, the real power is 3000x0.8=2400 Watt.

From the Pepco company, my bill is $530.40 (total usage is 4097 KWh) from 11/27/2014 to 12/16/2014.

Delivery Charges:
Distribution services:
Customer charge:                           = 7.39
Energy charge, first 800 KWH x 0.0272      = 21.76
Energe Charge, next 3297 Kwh x 0.0272       = 89.71
Franchise tax (delivery) at .00062 per kWH = 2.54
Universal service charge                     0.36
MD Environmental surchage .00015 per kWH   = 0.61
EmPower MD charge res .0037 per kWh        = 15.16
Gross Receipts tax  2.0408%                = 2.81
Montgomery city energy tax res .01131 per kWH = 46.34
Administrativ credit res .0002912 per kWH  = 1.19-
Subtotal                                      = 185.74 

Supply charges:
Generation services:
  Energy Charge  4097 kwh x 0.07732          = 316.78
  Procumental cost adj res .0005936 per kwh  = 2.43-
Transmission services:
  Energy charge  4097 kwh x .007250         = 29.70
 gross receipts tax at 2.0408%               = 0.61
Subtotal                                     = 344.66
Total                                        = 530.40

So it looks like the charge per kWH is about .0272 + .0037 + .01131 + .07732 + .00725 = 0.12678.

Some devices:

  • On my home server (idle most of time) with a cpu of AMD Phenom(tm) II X6 1055T Processor, it consumes 1.75kWh in 24 hours. Instantly Kill-a-watt shows 70+ Watt from the machine which makes sense (24 * 70 ~ 1750). So the yearly cost of leaving the machine on is about 1.75 * 365 * 0.12678 = 81. For HP chromebox (Intel Celeron 2955U Processor 1.4 GHz), the yearly cost is about 0.2 * 365 * 0.12678 = $9.25.
  • For Pi-top (+ Raspberry Pi 3), 11 hours is 0.06 kWh. 0.07 amp. 0.59 PF. 9 VA and 5 Watt (120v * 0.07amp * .59PF = 9VA * .59PF). For 24 hours, it consumes ~0.14kWh (vs 1.75 kWh in Phenom).
  • Raspberry Pi power consumption comparison
  • For raspberry pi zero w + Waveshare 2.7 e-paper running the clock weather application, it used up 6000 mAh @ 3.7A (4494mAH @ 4.94V)portable battery in 28 hours 40 minutes. 4494/28.67 = 156. Cf How much power does Pi Zero W use?.
  • For Intel NUC7PJYH, 24 hours is 0.09 kWh (including suspend after 2 hours). The idle power is 4W and using browser to watch Youtube is 9W.
  • For intel nuc8i5BEH (i5-8259U CPU @ 2.30GHz), 24 hours is 0.10 kWh. The idle power is 2W and watching youtube takes 7W.
  • For Intel i5-8500t (Dell Optiplex 5060 Micro/SFF), 24 hours is 0.18 kWh. The idle power is 7W when the host is running Proxmox 7.1-10 and two VMs (Ubuntu 20.04 & Win10).
  • For ASUS chromebox CN60 (i3-4010U) running the latest ChromeOS, 24 hours is 0.06 kWh.
  • UDOO 4W, SainSmart 9" LCD 3W.


How to Calculate Kilowatt Hours

SSD and HDD power comparison

How Much Electricity Each Item in Your House Uses

How Much Electricity Each Item in Your House Uses

How Much Does It Cost to Charge Your Smartphone for a Year

Best printers

The 5 Best Laser Printers Under $200 And Under

Brother MFC-L2710DW

Login: initpass See FAQ

Toner: TN760 - 3000 pages, $75. 3rd party.

Print page face down.

Laser Engraving Machine

Make your own laptop screen for Raspberry Pi

See raspi.tv


Blue Light Glasses

Do Blue Light Glasses Work? Everything You Need to Know

reMarkable 2

Best for note taking. See Remarkable.


Device DPI Resolution Video playing Browser
KindlePW (10th)
6' 8GB
300 ? X X
7.8" 2GB/64GB
300 1872 x 1404 Y XY
Boox Note Air
10.3" 3GB/32GB
227 1872 x 1404 XY Y

Note: 'X' means no good. 'Y' means good. 'XY' means mediocre.


  • Software download 下载 (not this old one)
    • Current Build number is 2.0.10 (2021-Jan). 2.0.11 (2021-June?)
    • Firmware upgrade with PhoenixSuit for Allwinner CPU if your Android is not 8.1.0. If your Android is 8.1.0, you can copy the update.zip file to sdCard/Download/upper directory. The local update will be able to scan the file from multiple locations.
  • Paperlike monitor - Windows is supported. For other OS, uses VirtualBox.
  • Second-Gen Dasung Paperlike E-ink Monitor May 2016
  • Paperlike Pro review. 40 refresh frame rate on HDMI.
  • Not-eReader: First E-ink Mobile-Phone Monitor. Received 2019-08-30 by DHL (shipped on 2019-08-28).
    • Can play youtube through 'Browser'
    • Youtube won't run without Google Play services, which are not supported by your device
    • No Google Play app
    • APKPure is included for users to install apps. Possibly download APK from Good e-Reader.
    • I install
      • VLC to play media files,
      • Firefox can install add-ons like uBlock Origin to handle ads like AdChoices,
      • Brave
      • Chromium
      • AirDroid to transfer files
      • Taiwan Radio to listen to Chinese radio stations
      • Digital Clock
      • File Explorder (copy APK from Android phone)
      • Gboard, Google Handwriting to input Traditional Chinese,
      • JuiceSSH for SSH (color theme for e-ink device, volume buttons to adjust font size). For some reason, I switch to use Termius
      • Doodling Around for drawing, RAM Booster,
      • Speed BOOSTER - Memory Cleaner & CPU Task Manager (Permit drawing over other apps).
      • Xodo Docs for PDF
      • EbookDroid
      • Twitter
      • Lynda.com
      • BBC News
      • MX Player Pro
      • TED
      • WiFi No Doze
      • Pocket
      • Squid
      • Nextcloud
      • DnsChanger, Nebulo
      • Vivaldi does not block AdChoices and the mobile version does not support extension (vivaldi://extensions will show 'This site can't be reached'). So I remove it.
    • "Files Go" is the default file manager. Another one is "Downloads".
    • User Manual icon leads to Dasung website for the manual.
    • Default reader is called "Dasung eReader". Uninstall it.
    • The "screensaver" is a Chinese Lunar Calendar which is cool for Chinese. It will update itself the next day (so it is not sleeping).
    • Android 6.0.1. Firmware version v2.1. Kernel version 3.10.65 root@ubuntu. Build number 1.0.17. 2GB memory, 64GB storage. Quadtex-A53. Battery 5600mAh. Display 1872x1404 (4:3) 7.8 inch (cf 1920x1080 is 16:9).
    • My settings:
      • Image III, Fast ++ speed
      • Display: Font size - normal (Large, Huge, Biggest)
      • Accessibility: Large text: on
      • Brave browser -> Accessibility: Text scaling 120%
      • Firefox -> Settings -> Accessibility. Use system font size: on. Always enable zoom: on.
      • Display sleep after 30 minutes of inactivity
      • Font size: Normal
    • Dasung Not e-Reader Review on mobileread
    • https://youtu.be/nTk5bwBxt9Q A video from youtube Oct 2019

Kindle DX as an external monitor

Traveler: Ultimate Distraction-Free Writing Tool


Onyx Boox Mira 13.3 monitor


Onyx Boox Note

Settings and launcher

Seeking Recommendations for Simple Apps to Enable Full/Hidden Android Settings

Transfer files


File Transfer File Transfer via SFTP

File Transfer via SCP

scp -v ~/Desktop/book.epub [email protected]:
scp -rv [email protected]:/opt ~/Downloads/

Making Local Backups

mkdir -p remarkable-backup/files
scp -r root@remarkable:~/.local/share/remarkable/xochitl/ remarkable-backup/files/
scp root@remarkable:~/.config/remarkable/xochitl.conf remarkable-backup/
scp root@remarkable:/usr/bin/xochitl remarkable-backup/

Transfer notes

Transferring note files to computer?


Useful apps


EMR technology

Second display

Anyone use their Boox Note Air 2 as a secondary display? I keep it open with spacedesk next to my monitor so I can drag and drop things onto it to read rather than read it on my backlit monitor.

Bluetooth keyboard

Hide virtual keyboard when a bluetooth keyboard is connected



Notes from the Manual.

Lasso tool

Yes, we can copy an area and paste it onto another NotePad. The trick is after we copy an area, in the different NotePad we should click on the 'Lasso' tool again in order to see the 'paste' icon to perform the operation.

NotePad template

Click on 'More' and select 'Layer'. From there you can see "Layer 1" and "Templates_Blank(Portrait)". Click on "Templates_Blank(Portrait)" and scroll to the next page (Bottom-right arrow key). I choose 'Horizontal Lines 16' for my like.

Note Air

  • https://www.boox.com/noteair/
  • It seems FAT32 format works for OTG flash drive, but not exFAT or EXT4.
  • How do you hard reset the Note Air? Power off the device, do not connect a USB or power cable Hold down the power button, continue to hold it Wait until the small blue power LED inside the button turns on, and continue to hold for about 7 seconds Release the power button, and press it exactly 5 times.
  • Enabling Google Play store works.
  • 15 Tips and Tricks for Onyx Boox Android eReaders. Power option: Go to Settings > Power > Power off Timeout -> Never.
  • Why the Notes app does not have a highlighter pen?
  • Onyx Boox Note Air Review with 10.3" E Ink Screen
  • File transfer
    • Transfer Books app. All files will be in a folder 'Internal shared storage' -> WifiTransfer (not 'Download')
    • Autosync and run it through OneDrive/dropbox/google drive. It synced two direcories.
  • Font issue
  • Refresh mode adjustable from E-inkCenter (Pinch to Zoom in normal, speed, A2, and X modes on Onyx Boox Note Air )
    • Normal mode: suitable for general text reading (left most icon)
    • Speed mode: quickly reading images & text
    • A2 mode: scrolling pages with images & text (still feel slow)
    • X mode: web pages and video (best speed although black font becomes gray)
  • When I pinch to zoom in, suppose I zoom in to the left side, then clicking on the right area won't allow me to navigate the right side of the PDF file; it stays on the left side only. See this video. So probably it's still better to use the "Article mode" for reading technical papers.

Note Plus

New firmware updates

Onyx Boox issues 3.2 update for previous generation hardware

Swap and memory

speed up Boox with swap

Pi-Hole Blacklist for BOOX devices

  • Pi-Hole Blacklist for BOOX devices
  • index1.send2boox.com, push.boox.com, en-data.boox.com (升級服務器), cb.boox.com (?), en-rom.boox.com (?) from pi-hole log on 2/4/2023.


Hardware spec (page 97 of the manual): 13.3 inch & 2200 x 1650 pixel, CPU is 1GZ, Ram is 1GB LPDDR2, Android 4.0.4, 16GB storage, 1.21 lbs (ipad 9.7in 2017 is 1.03 lbs). Very comfortable when I use it to read technical papers. It does not have front light, unfortunately. Shipping took about 2.5 weeks.

The manual is written in simplified Chinese only:) It is lightweight. Writing on the ereader is OK. Got it from banggood.com.

Onyx Boox Max Carta vs Onyx Boox MAX2


Max2 has a micro HDMI port.

Boox as a Second Monitor

Boox and SSH terminal

I found using Max Carta to do work on a terminal is OK.

First go to the Play Store to download an SSH client. I am using JuiceSSH.

We can adjust font size and the theme (white as the background). Even you have connected to a host, you can still use the volume +/- to increate/decrease font size on-the-fly.

You cannot rotate the screen however.

I am using a bluetooth keyboard. If I don't use the keyboard for a couple of minutes, it'll take a few seconds for the device to respond to my typing.

When I use nano, the color syntax highlight is not good. So I use nano -Ynone FILENAME to disable the syntax highlight.


Airdroid works for transferring files between Boox and computers in the same network.

Boox and remote desktop

Note the the device has locked to rotate the screen (i.e. the screen rotation app from Play Store does not work)

When testing to connect to a Windows Desktop

  • Microsoft remote desktop does rotate the screen but it does not respond to my clicking
  • bVNC does not rotate the screen

Open html files

If I made a copy of a website (efficient R programming for example), then use Boox's default browser to open the html file, some links do not work.

Open epub files

  • FBReader: no TOC
  • NEO Reader v2.0: *TOC works*
  • Onyx Neo Reader: format is OK, but not TOC
  • OReader: no TOC

Open pdf files

  • Neo Reader v2.0: TOC & search work! We can use the 'Crop Page' function to remove blank space on sides.
  • Onyx Neo Reader: no TOC

PDF format has an advantage over epub: mathematical notation is guaranteed.


Notes we created cannot be seen from Storage > sdcard > note directly. In order for the notes to be seen there (so we can copy them to computers through AirDroid), we need to click on each note and choose the gear icon and pick "Export the current page" or "Export all pages".


The default music player works fine. I also like VLC downloaded from Play Store.



Date Automatic date & time: uncheck

Power Management

  • Sleep: 30 seconds
  • Power off timeout: 60 minutes
  • Network Inactivity Timeout: 15 minutes

microSD card To eject it, go to Settings > Storage > Unmount SD card.

Reset the firmware Settings > Privacy > Factory data reset.

User Setting

  • Open the last read document: uncheck
  • Homepage preference: Show new added books
  • Show books' titles instead of their names in library: uncheck


Language Hacker's Keyboard


Appplication Setting

  • USB debuggin
  • Manage apps

DRM Setting Adobe ID




Wireless Setting



Device status

  • Battery level
  • IP address

System Update

  • Model number: MaxCarta
  • Build number: 2017-04-28_18-25_1.8.2_e4efe5. There is a button to "Check update from local storage".

Android version 4.0.4

Android apps

I installed

  • AirDroid
  • Device Info-HW
  • Dolphin
  • Hacker's Keyboard
  • JuiceSSH. For some reason, I cannot connect to my bluetooth keyboard. So the app is not useful.
  • VLC. It provides a loop function. However like the default 'Music' player, when I play a music, it will have a hiccup every few seconds.

Conclusion: it is best to use the device for viewing documents only.

Kindle Lite

Not compatible with Boox Max Carta Android 4.0.4. According to this, Android 4.1 is required. This source said the app is best supported with an android device of version 4.4. Android 4.4 seems to be required for other Android apps to work according to Good e-Reader.

Regular Amazon Kindle app. Not responding.

Android 4.4


Boox Tab X 13.3

Onyx Boox Tab X Review: 13.3" Paper-Like Productivity Powerhouse

Kobo ereader

I have a Kobo Aura HD. The touch screen is controlled by infrared (like the Nook Simple Touch, no requiring electrical conductivity), not capacitive or resistive technologies. Even a paper or an eraser works on the touch screen. Its screen is 6.8 inch, 1440 x 1080-pixel display with 265 dpi. The brightness is 326 lux. The built-in front light comes the light technology from the ComfortLight. It directs light at the page and boasts an even distribution across the display. The microSD slot can add up to 32GB to the built-in 4GB of storage. The exact model is not on sale now because it is replaced by H2O.

Firmware download

Kobo Wifi Weather Forecast



The pdf program is not quite useful for scientific papers.

Alternatively, we can try KOReader. Currently my Kobo FW is 3.18.0 (9/23/2015). I am following the procedures on KOReader's Kobo devices page.

  1. Go to here and download <KBStartMenu_07inclUp4.zip>. Extract the folder kbmenupngs (it contains png files) and put it to the root folder of Kobo. Also put KoboRoot.tgz to .kobo hidden directory (putting it onto .adds won't work). Reject and reboot.
  2. Download <koreader-kobo-arm-linux-gnueabihf-v2014.04> from v2014.04-stable github page. Put koreader folder in the .kobo hidden directory. Ignore the png file and KoboRoot.tgz file there. Reject and reboot.

If something goes wrong, we can go to Settings -> Device information -> Factory reset to reset the system. It can also download the update after the wifi configuration is set up.

When you update koreader, it should be sufficient to extract the koreader folder, without KoboRoot.tgz - that one is needed to add the launcher.

Standby does not work out of box. See http://www.mobileread.com/forums/showthread.php?t=216960&page=85. That is, run

nano -c /media/brb/KOBOeReader/.kobo/koreader/frontend/ui/uimanager.lua

and change the Standby value from 1 to 4 and suspend function call from 0.5 to 2. The standby problem is resolved.

Battery always 100% (too good to be true, I have not used the ereader for a while). http://www.mobileread.com/forums/showthread.php?t=220912. It`ll take care of itself after a few charge cycles.

.kobo folder after reset

After I run factory reset on the device (and plug in it to my computer), I see the device only has 3 hidden directories

brb@brb-P45T-A:~$ ls -la /media/brb/KOBOeReader/
total 20
drwx------  5 brb brb  4096 Dec 31  1969 .
drwxr-x---+ 4 brb root 4096 Oct 11 10:22 ..
drwx------  2 brb brb  4096 Oct 11  2015 .adobe-digital-editions
drwx------  7 brb brb  4096 Oct 11  2015 .kobo
drwx------  8 brb brb  4096 Oct 11  2015 .kobo-images
brb@brb-P45T-A:~$ ls -la /media/brb/KOBOeReader/.kobo
total 152
drwx------ 7 brb brb   4096 Oct 11  2015 .
drwx------ 5 brb brb   4096 Dec 31  1969 ..
-rw-r--r-- 1 brb brb     25 Oct 11  2015 affiliate.conf
drwx------ 2 brb brb   4096 Oct 11  2015 certificates
-rw-r--r-- 1 brb brb     76 Oct 11  2015 device.salt.conf
drwx------ 2 brb brb   4096 Oct 11  2015 dict
drwx------ 2 brb brb   4096 Oct 11  2015 kepub
drwx------ 2 brb brb   4096 Oct 11  2015 Kobo
-rw-r--r-- 1 brb brb 110592 Oct 11  2015 KoboReader.sqlite
drwx------ 6 brb brb   4096 Feb 28  2013 slideshow
-rw-r--r-- 1 brb brb   3298 Oct 11  2015 Trolltech.conf
-rw-r--r-- 1 brb brb     84 Oct 11  2015 version
brb@brb-P45T-A:~$ ls -la /media/brb/KOBOeReader/.kobo-images/
total 32
drwx------ 8 brb brb 4096 Oct 11  2015 .
drwx------ 5 brb brb 4096 Dec 31  1969 ..
drwx------ 3 brb brb 4096 Oct 11  2015 132
drwx------ 3 brb brb 4096 Oct 11  2015 18
drwx------ 3 brb brb 4096 Oct 11  2015 213
drwx------ 3 brb brb 4096 Oct 11  2015 233
drwx------ 3 brb brb 4096 Oct 11  2015 66
drwx------ 3 brb brb 4096 Oct 11  2015 70


KOReader supports any Stardict format dictionaries. To use that, we need to download and put the dictionary 'folder' in the right place (.kobo/koreader/data/dict) of the Kobo ereader.

I tried two dictionaries (Longman Dictionary of Contemporary English and cdict-big5 dictionary) from http://abloz.com/huzheng/stardict-dic/. And they work fine.

Turn your Kobo into a Debian Linux tablet


Flexible E-ink


Multiple ethernet ports

Power over Ethernet (PoE)

Some devices powered by PoE include VoIP phone, IP camera, wireless access point. router.


Type-C Multi-Port Adapter

Trendent USB to ethernet adapter

ASIX AX88772A. The windows driver can be found on axix.com.tw. The one from Trendent website does not work.

USB OTG (On-The-Go) adapter

Fast charging

Fast Charging Standards Compared: What Is Your Phone Using?

DisplayPort Over USB-C

What Is DisplayPort Over USB-C and How Does It Work?

Magnetic Braided USB Charging Cable


Adding USB 3.0 ports to an old PC

USB Video capture

USB condom

Why Your Phone Charging Cable Needs a USB Condom. The USB condom is an adapter you place between the USB port and the charger side of your USB cable. Inside the adapter plug, the data “pins” are missing.

How to Crimp Your Own Custom Ethernet Cables of Any Length


Wake-on LAN

What Is Wake-on-LAN, and How Do I Enable It?

How to park your car on a hill


When parking your car on a hill, put the car in neutral, set the emergency brake, then put the car in park (or in gear). This puts the weight of the car on the emergency brake rather than the transmission and can extend the life of your transmission.



Optical Network Terminal (ONT)


Do I Need a Firewall if I Have a Router?. If you already have a router, leaving the Windows firewall enabled provides you with security benefits with no real performance cost. Therefore, it’s a good idea to run both.

Difference Between Routers, Hubs, and Switches

What's the Difference Between Routers, Hubs, and Switches?



  • Prioritize by Service
  • Prioritize by Interface
  • Prioritize by Device with IP Addresses
  • Prioritize by Device with MAC Addresses

WPS (Wi-Fi Protected Setup)



2.4GHz, 5GHz

What Is the Difference Between 2.4GHz and 5GHz Wi-Fi Bands?

Wifi and health


Wifi and Microwaves

Why Does Wi-Fi Use the Same Frequency as Microwaves?

Wi-Fi Extender, Mesh Network, Booster, Repeater

Google wifi OnHub, Nest Wifi

Google Is Killing OnHub: Here's What Users Need to Know


How to Install Homebrew on a Nintendo Wii Using LetterBomb

Logitech Unifying Software


ChromeOS version works fine.


Bluetooth adapter

The Best Bluetooth Adapters For Your TV, Stereo, And Speakers


SAR levels


How to silence your computer mouse

An easy way to take off the cape of the rectangle box is to use a pairs of long nose pliers instead of a knife. The method works on my Logitech M210 mouse. The trick is to shorten the click distance.

Best bluetooth mouse


Logitech M720 Triathalon Multi-Device Wireless Mouse

Logi M590

  • Silent mouse. Other silent mouses include M330, M350, M585.
  • Channel 1 is USB, Channel 2 is Bluetooth
  • Once you switch to Channel 2, hold the button for 5 seconds and it will enter a pairing mode.
  • This method works on Ubuntu and Lubuntu 18.04.

Laggy bluetooth mouse logitech M585/M590. Note that the original file contains "ConnectionParameters" section already. The original Latency is 44 and MaxInterval=9. I am using Ubuntu 20.04 (Pop_OS).

Logitech M650 Small/medium size. Quiet.

Mouse Acceleration vs Sensitivity


Sensitivity/Speed is how far you have to move the mouse to move the pointer a particular distance. A high speed means that very small movements will shoot the cursor a large distance.

Acceleration is a very clever optimization. Normally, to keep precision control over the cursor (for those who need it) you need to keep the speed pretty low. But this means that if you need to get to the other side of the screen, you need to slide the mouse annoyingly far. Acceleration lets you have the best of both worlds.

What acceleration does is boost the speed temporarily when you 'flick' the mouse. So if you need to get to the other side of the screen, you can flick the mouse quickly just a short distance and the cursor will move much further. You then switch to moving more slowly to get the cursor exactly where you want it.

On Linux Mint, I can change these two settings individually. I use medium for the sensitivity and 3/4 high for acceleration.

Gaming mouse and DPI


Compact keyboards

8 Compact Keyboards to Save Some Disk Space

Anker A7721

Manual & amazon.

  • One complain is it goes to sleep quickly (5 minutes). So macOS will show keyboard is disconnected frequently.
  • Press FN + Z to put into pairing mode
  • Lots of tips including how to reset the keyboard

Logitech wireless solar keyboard k750

One problem is there is no Num Lock and Caps indicator on the keyboard unless you have install Logitech SetPoint software (Windows & ChromeOS).


  • A review on 2016.
  • Manual from logitech.com.
  • Tips:
    • To enter a pairing mode: press and hold one of the easy-switch keys for 3 seconds.
    • To switch devices: press one of the easy-switch keys quickly.
    • The keyboard has a true 'del' key (in add'l to the back key). On regular mac keyboard, you have to use fn+delete to perform the regular delete action.
    • The fn and ctrl keys position are reversed on K780 compared to the regular mac keyboard.
    • fn and del = print screen
    • cmd and left/right arrow = HOME/END

Logitech K380 Multi-Device Bluetooth Keyboard


Lenovo ThinkPad Compact USB Keyboard with TrackPoint

Lenovo Thinkpad Keyboard 2

Keyboard with touchpad

AmazonBasics Wireless Keyboard with Touchpad for Smart TV - US Layout

Microsoft all in one keyboard

Microsoft Wireless All-In-One Media Keyboard



A bluetooth based gadget to control a windows/android/ios device. See http://qblinks.com/support

How to Replace an Outlet That’s Controlled by a Light Switch


GFCI outlet

Why Your Electrical Stuff Sometimes Stops Working Until You Push the Magic Red Button

How to Ship Packages Without Leaving Your House




The Best Sit/Stand Desk Converters And Risers For Your Traditional Desk

Dell PowerEdge R630 server

iPad 9.7 2017 (5th)


Rocketbook Erasable, Reusable Wirebound Notebook - Letter Size

Drawing tablet

XP Pen Artist 15.6 Pro

Samsung galaxy s6 lite

Laptop battery

  • Should I Remove My Laptop Battery To Increase its Life? It really depends on the voltage cutoff of the device in question.
  • The Formula for Estimating Laptop Battery Life. Just divide your computer battery’s watt-hours by your estimated wattage. The result is the number of hours you can expect your battery to last. Your expected wattage varies depending on the task you’re performing. Gaming will use between 40 and 60 watts, watching video will consume 15 to 30 watts, and web browsing will eat 10 to 15 watts.

Battery Life

Watch battery

  • Casio Men's MRW-S300H-1BVCF: Rechargeable battery life is about 10 years
  • Casio Women's LA20WH-1ACF : CR1616 3V, 5 years

CR2032 battery

Used in PC, car remote, ...

Homopolar motor

How to Make a Homopolar Motor

Govee Wi-Fi Temperature and Humidity Monitor

No More Dead Plants, with The Govee Wi-Fi Temperature and Humidity Monitor

Google voice & Obihai

Outgoing calls stopped working on GV TCP connection to failed. Dec 2017.

Port Your Mobile Number to Google Voice

How to Port Your Mobile Number to Google Voice

Burr coffee grinder


The 8 Best Online Shopping Sites for Cheap Electronics

How to Spruce Up Your Office Desk

How to Spruce Up Your Office Desk