BIOS Updates forum

Years ago I was tech smart, I understood all about how my 486 MOBO worked, and my brand new PnP ISA cards, etc. I was a DOS programmer (MASM) also. But I have ignored tech advances for about the last 10 years. My conceptual knowledge is still good, but my detailed knowledge is very out of date. Also my brain is not very sharp anymore. I have some GENERAL QUESTIONS about how things work these days. Maybe someone here will answer some of the questions or tell me a webpage where the operation of modern day systems is explained.

Q1) Are the 'Boot Block' functions = run POST, read CMOS, setup IVT, find boot device ? Apparently they keep that basic stuff separated out from the modern stuff (PCI, ACPI, etc), so you are able to run through a Boot Block Recovery.

Q2) Is any information actually kept in the 'CMOS' data area ? There is so much more information to store now. The CMOS area was small. I assume the CMOS area isn't even used any more. l assume that the many additional (new) parameters are written to the EEPROM. I would guess CMOS isn't needed anymore except as a battery operated clock.

Q3) The EEPROM is divided into Boot Block, BIOS, ESCD and DMI data area. I saw that the flash programs have command line switches that allow you to clear or rewrite those areas. But then I saw AWARD flash program has all of those options PLUS an option ( /PY ) called PROGRAM FLASH MEMORY and ( /PN ) called DO NOT PROGRAM FLASH MEMORY. That leads me to believe there is some additional area besides BB, BIOS, ESCD and DMI. What does it mean?

Q4) HELP ! Please tell me if there is a website that explains how modern BIOS is layed out, a general flow of the boot sequence, etc. Preferably an explanation that doesn't require reading assembly code.

Thanks for your help.

Bill S. - in Seattle, WA, USA

Q1) Bootblock checks the checksum of the main BIOS and goes into recovery mode if it's bad. If it's good, the main BIOS is decompressed into memory and executed there.
Q2) Yes, CMOS is still used. On newer chipsets, it's 256 bytes which is a lot of space for BIOS settings.
Q3) Most flash ROM chips are divided into sectors - either equally sized or variable sized. If you want to overwrite a part of the flash ROM chip, whole sector must be erased and reprogrammed. So ESCD and DMI are often placed into separate sectors. Bootblock too. Some flash ROM chips have protection methods that can prevent the bootblock from being modified.