What is the purpose of two bios chips on laptop motherboards?

[myth77]

I ve noticed that on the newer laptop boards there is often two bios chips! For instance, on asus g751 which has gpu and cpu soldered you can find two bios chips, and for instance on asus g750 there is also two, but one on the mainboard and second on the gpu board. For this g750 model there is gpu card, the chip is not soldered to the board...
So i am wondering what is the purpose of two bios chips? Is second only a backup, or it is responsible for some other things? Strange is that you can also see it on the gpu card...
Please explain it to me

[jeremykum]

Re: What is the purpose of two bios chips on laptop motherboards?

So far it isn't for backup purpose.

Generally newer generations uses 2 sets of bios.
1. Main bios (might includes Intel ME Firmware inside)
2. EC bios

You may find sometimes, those bios chip could have same code (hence same capacity) or different codes.

If I have not mistaken, starting from 4th Gen Intel Core i (Haswell), designers started to integrate the EC bios into the KBC chip, hence more difficult for reprogramming if you are unable to boot up the laptop.

Some may have a 3rd bios chip. For USB 3.0 purpose.

As for GPU, not necessarily need a stand alone bios, most design are integrated to the Main Bios.

Best way is you refer to the schematic for confirmation.

[myth77]

Re: What is the purpose of two bios chips on laptop motherboards?

OK i attached for asus g751 boardview and i zoomed those two bios chips on boardviewer. Can you please tell me what is their function on the board? I believe that U2801 should be main bios...but what is then U9402? please explanation...

[myth77]

Re: What is the purpose of two bios chips on laptop motherboards?

Anyone?

[subroto]

Re: What is the purpose of two bios chips on laptop motherboards?

Tell me the chip number of two different EEPROM. I'll tell you the the main BIOS number and EC BIOS number. Usually EC ROM number is like 25x20, 25x40, 25x80 etc. And main one like 25x16, 25x32, 25x64 etc. You may now differentiate between EX and Main BIOS.

[myth77]

Re: What is the purpose of two bios chips on laptop motherboards?

As you can see in the images attached, in the right corner, first chip is winbond W25Q64FVSSIQ and second is winbond W25X40CLSNIG. so the first one would be main and second EC ROM?

[samanthban]

Re: What is the purpose of two bios chips on laptop motherboards?

W25Q64FVSSIQ - main
W25X40CLSNIG.- ec

[ala_borbe]

Re: What is the purpose of two bios chips on laptop motherboards?

size of chip does not determine role... eprom chip stores data for some external chip to use it, so it could be anything... you can put mp3 song on it if its small enough

real use for the chip varys from a machine to machine but content can only be disassembled with some decompiler like IDA PRO or some other tool
even then you have to know arhitecture of chip to disassemble or modify

this is how whitelist bios are created or unlocked advanced menus for some boards

so to conclude, eprom can store any data, its like a mini hard drive or mini usb stick