Recently I went into a very, very strange problem. I have a RAID5 disk array in my home PC based on SB8xx AMD controller. Recently I bought a brand new graphics card to my computer. After replacing my old one to my horror I noticed, that BIOS does not see any of my hard drives plugged into my built-in RAID controller on my ASUS motherboard. I was shocked, that replacing a video card can lead to such problems with my RAID (what the hell?). I would never suspect that I can lost my hard drives after replacing a video card…
Fortunately it was not as bad as I firstly thought. The raid was not seen by the BIOS itself, thats true, however the operating system did see my RAID array without any problems – like nothing happened. I only lost the boot availability from any hard drives which were connected to my RAID controller.
First thing I did was to change my system hard drive mode from RAID to IDE in system BIOS. That allowed me to boot my system and after that the system saw my RAID array without any problems. That was a relief, because I thought that I have lost my array together with the data contained within.
But that was no solution to me, because the system hard drive operating in IDE mode works noticeably slower and I did not buy an expensive video card to slow down my computer!
Then I started thinking what could have caused such strange behavior. I tried upgrading the BIOS but that did nothing. Then I recalled, that the system BIOS is mapping boot roms of hardware within a special memory, called a Conventional Memory which is always 640KB in size. So maybe the system BIOS has wrongly mapped the roms and not all of them fit into 640KB? And that was it! Disabling some built-in roms (in my case I disabled buil-in IDE BIOS ROM because I do not boot from IDE devices normally) did the trick – the system BIOS started to see my RAID array again. Uff.
So if anyone would ever go into similar problems after replacing a video card – to workaround the issue you will have to disable some unused built-in roms in BIOS setup to allow RAID BOOT ROM to fit into conventional memory and be seen by the system BIOS.