Sharing RAM with Graphics

jimbo45 · 20 May 2009

Hi all
Note that the OS CAN and DOES make BIOS calls while booting (and even after it's booted).

The BIOS is only another "micro OS" itself. Now W7 (or any other OS) can't make any changes in ROM of course some settings in the BIOS could be temporarily changed for the life of that Boot.

I'm not sure how the code works as you'd have to "disassemble" the BIOS code to see exactly what's happening but it *could* be possible that some "start up parameters" temporarily change the standard Bios parameters.

Some while ago (haven't seen it for a while but it could still exist) Windows used to be able to use "Shadow memory" where the BIOS code was copied into the Windows Low (or High - can't remember now) protected memory area since the Internal RAM of the computer was actually faster than the speed of the ROM access.

If W7 uses this type of technique it COULD alter values to suit itself unless the user explicitly sets values at boot.

Cheers
jimbo

Captain Zero · 20 May 2009

An OS can boot and alter the BIOS? Sorry but, no way. Not anymore, we have Intel TX, Windows 95 and Chernobyl to thank for that.

It will address that shadow ram you're referring to but only after the BIOS puts it there. Those 'registers' tell the OS what's plugged in and how it's configured. At no time does the OS actually WRITE or ALTER the BIOS itself. That's simply not accurate.