Does the BIOS get used after bootup?

[Gustavus]

I thought the BIOS was only used during bootup -- but I have a strange problem that now makes me think that may not be right.

I have an older machine built on an ABIT IS7-E motherboard running Windows XP with SP3. The CPU is an overclocked Intel Prescott 3Ghz. It has been stable for years but began rebooting on it's own from time to time. No overheating -- CPU cooled with a humungous Thermalright cooler, Northbridge cooled with the Thermalright H03 active cooler, heatsinks on everything in sight etc. It simply does not get hot, not even slightly hot. The power supply is a new OCZ 500W which is loafing under the load this old system puts on it.

Each time it rebooted on its own, on bootup the BIOS had been cleared to default. I finally managed to get a diagnostic saying the CMOS checksum had failed and the BIOS was being reset to default. I had recently replaced the CR 2032 lithium cell, but just in case bought a new one and replaced it again. If I either restarted the machine or started it from being normally shut down, I did not get the checksum error and the machine booted normally.

It is unlikely that memory is the problem since the OCZ Platinum revision 2 memory will run Memtest for 24 hours with no problems.

I have run Prime95 for many hours, computed Pi to a million places over and over with no problem. Appears to be rock stable, and then it will reboot.

Does a machine ever access the BIOS after it has booted into the OS?

Thanks.

 

[pcgeek11]

The BIOS and SRAM Data is loaded into System RAM at boot and this information is used when the PC is running, but it isn't read again from CMOS or SRAM after it loaded into memory.

Here is a breakdown of what the motherboard BIOS actually consists of:

Power-on diagnostic tests

System configuration utility

Bootstrap loader

BIOS interface

When you boot up the computer, it initiates the POST (Power-On Diagnostic Test). The POST serves as a quick-and-dirty way to make sure that all the critical components are functioning.

After the POST sequence completes, you are given the opportunity to access the system configuration utility. This utility allows you to configure and modify a range of features. These BIOS features show you just how important the BIOS is.

These BIOS features control every aspect of the computer, from the speed at which the processor runs to the transfer mode of the hard disk. It goes without saying that these BIOS features are the reason why I'm writing this book. We go into details later in Chapter 4.

After the short delay, the BIOS starts the bootstrap loader routine, which scans for a valid master boot sector on all available drives. This can be anything from a hard disk to a CD-ROM drive. The master boot sector is just a predetermined area containing code that initiates the loading of the operating system.

When executed, the master boot sector turns over the booting process to the operating system by loading the operating system's boot sector. The operating system then starts loading up its core files.

In most cases, this is where the BIOS' role ends because current operating systems employ their own 32-bit or 64-bit drivers, which offer far superior functionality and performance to the BIOS' basic drivers. However, the BIOS' core drivers still have some importance.

 

[Gustavus]

pcgeek11

Thanks for the very thorough explanation. I will print it and keep a copy in my notebook. I still have no idea of why the system fails occasionally and then reports the CMOS check sum failed etc. My experience in the past was that was generally due to the battery starting to go bad -- but as I said I have replaced it twice with newly purchased batteries. One was a Maxell and the one in there now is an Energizer so there is no commonality there.

I have another machine based on an ABIT IC7 G which uses the same pair of OCZ Platinum revision 2 2,2,2,5 PC3200 modules so will swap memory modules between the machines and run more tests to see if the problem persists.

Thanks again. Your reply is much appreciated.