EEPROM BIOS Firmware flashing, the good , the bad and the ugly.   
 
Or how to Brick a PC easy?

Most folks that do this (noobs) end up bricking their PC; see why here.

Best practice is leave it alone!

This job is to upgrade your BIOS Firmware,  located in flash memory.
The word flashing is a verb, the act of burning the EEPROM with new BIOS code.

How to brick you PC easy 101?:

Rule1: Do so only if the PC has issues, if the PC ran ok for 1year,why in the world blame BIOS?, after all it does not leak out of the chip, it lasts for 100 years by design. (hint: leave it be )
  1. You think all PCs are the same so therefore your BIOS binary is the same , wrong!, you must get the exact BIOS binary for your EXACT model and sub model motherboard. (ask your OEM maker first)
  2.  I use USP power supply to Flash any Desktop,  on Laptop a known good battery (large) inside can serve the same role here,  no AC power failures allowed, or the flash burn can brick the PC easy.
  3.  Ask a real PC technician to do this?
  4. Do not flash PCs that are sick  that for example have power problem, or dead screens.
  5. Some motherboards (vast) have  5 to 10 sub models, and if  you guess wrong,  and say (examples)the mobo has AMD chips and you mess up and use the Intel or Nvidia GPU version now the BIOS is dead.
  6. In all cases if you are super compelled, to flash upgrade your BIOS, do go to there makers website.com and ask them for help. (yah think?)
  7. Learn 1 thing first the best way to FLASH  is to use the actual BIOS featured, flash update page inside BIOS, (if it has one) the next best way is to FLASH under DOS, (FREEDOS)
  8. Never flash while booted to WINDOWS (some exceptions exist ) some OEM run the flash.exe from the desktop then cold boot the PC and it runs in runonce box that shuts off all other processes. 
  9. This above #8 is real risky , if the HDD is bad or windows corrupted, the Flash is DOOMED.  (so is dumb to do , by you are the OEM !)
  10. The best way to FLASH is off  a USB STICK memory  booted, demand that or make it so if you can, as I have many times. (ez-flash is best , 2nd best is FREEDOS flashed)

Some good reason to flash BIOS?
  • To gain support for newer and faster CPU or more cores in your processor. (mostly on gaming PCs or high end enterprise PCs)
  • To gain support for newer and higher density DDR RAM.
  • To fix a specific bug in your BIOS for a failing chip or device. (like adding USB3  support inside BIOS and booting to USB devices, etc.)
  • To make UEFI work right, some PCs have 15 upgrades  just for STINKING UEFI that are full of nasty bugs. (I avoid UEFI until I think it is stable)

My HP PC flashes from FREEDOS, a wise choice by HP.com (w10 )  (but the best is always the BIOS ez-flash seen on many newer PCs,  this is BIOS burns BIOS mode. (super safe; this is)


Below is my expanded list of how to fail,  (I'm the guy that had to fix the dead PC after others messed this up for 20 years ( even back to EPROM days 1990 and older, UV Erased)

BIOS FLASHING,  

Flashing can be easy sure!, but is loaded with RISK: ( the older the PC; the more risk)
If you play with BIOS flashing it, then kill it dead,  what is your PLAN B? Oops a Daisy , I killed it dead., now what?
Some folks have a bad PC, and flash it first thing they do, now the PC is DOUBLE dead, and your technician gets it and is super confused, Yah think?

POINTS TO PONDER FIRST:

The Computer must compute, that means with no errors.!   (many things can fail here with 3 billion transistors or more...)
Are you in the middle of some huge lightning storm? (stop and wait for it to end)
The PC must not have bad batteries inside or attached ! That includes the RTC NVRAM COIN CELL too.
I use a UPS  AC power supply on all DESKTOPS flashed, if a Laptop I test the HELL out of the main battery for leave it out and  run a UPS.
If you don't have a UPS try this generator. (full tank of fuel , lol)
Do not flash if your CPU processor is overheating and if filthy inside,
That includes bad RAM . ( if the OS  BSOD's consider not flashing BIOS now)
Do not flash if you think any modules in the PC are suspected to be bad for sure shorting ANY POWER RAILS.
Do not flash until a OEM PC makers real technician agrees or gives you the correct version and perfectly matching BINARY files.  (or you will brick the PC)
Just one model of PC may have a mobo version with AMD or intel processor or 4 different GPU chips  used and if you get the wrong BINARY  you just bricked the PC (if lucky the old one will re-flash ok).
Do not attempt to use external USB HUB's to boot your flashing stick,  of any kind , only use the direct USB jacks on the PC when flashing.
USE the USB2 jacks, flashing not USB3 on 10 year old PCs.
Make sure you learn how to boot USB memory sticks on your PC, some PCs this is turned off in BIOS, so turn on USB ports all and turn on legacy mode for USB inside BIOS first. (and boot priority to USB first)
Last, never flash under WINDOWS directly ! EVER.  (while in the desktop environment)
I like to strip my PC down to a minimum system before flashing, even pulling the HDD and DVD drive, and for sure bad batteries replaced!
The best ways to flash, are:

Do not take risks and flash without making 100% sure your binary files (newbios.bin) matches your exact PC model and submodel or even your country.

Here is me flashing and HP computer, using the HP Freedos way.
This is by far the best way to FLASH! (under DOS)
Here is ASUS.com Ez-flash ( yes, the best way) You can do this with no CD/DVD or HDD of any kind in the PC, after those things can fail , use  USB stick for the flash.bin file. 

This runs in Intel "REAL" mode, and is 100% safe, the most safe way on earth to flash is with EZ-flash.
if you can make sure you backup your old BIOS first or download say the top 10 versions just in case.
Why so many well the makers of those files assume at lease a base version is in place. (some OEM do not even explain this, nor even tell you what each version, what the update does !)


more FREEDOS examples.
8540w actual.

Each PC maker has there own way to flash the BIOS. (some are good others are vary risky)


Flashing means or burning, is  to charge up the EEPROM cells gates.  A.K.A. programming or burning and  in the very old days' fusing the PROM's)  EE = electrically erasable and alterable.
This gate is like a very tiny capacitor that charged up with electrons. This is how 1 binary bit is stored,
This chip does not forget or leak bits to the bytebucket at all.
Flashing is the ACT of charging the GATES of this transistor (millions of them)
The term Flash was used when EEPROM started at  Intel or SEEQ. (they were slow to burn so when they learned how to make them faster way way faster the word FLASH was termed and bragged about, for good reasons.
The FLASH simply charges up the MOS floating gates. (after erasure)  this is just ONE BIT CELL. (1 of 8 million on mine)
This cell charge can LAST  for 200 years. (from top makers like Microchip(tm) "data retention spec. shows 200 years." End CMOS101.
They have oxide layer under the gate that is super impurity free !  ( mostly job#1 on all CMOS made) this!
Below is  a typical EEPROM used today, and has no socket. (sadly)
Q16 is 16 Million BITS Q25 IS  512 million bits. (modern serial EPROMs called SPI)


version 2  5-9-2017   12-12-2018 removed all HP examples and made this more generic; and shorter.
 ( I have flashed 100s of computers and before EEPROM we had UV erased EPROM and I did hundreds of those too, (even with spare chips in hand)