I have a damaged BIOS chip on my PC Chips M575 and I'm looking for a replacement. Based on the markings, it appears to be the classic PC Chips rebranded special. The chip says H.T. M21084 T9746, but its ID shows as (C2 1A) on my TL866 programmer and UNIFLASH reports it as a Macronix MX28F1000P/12 - sectored: 7x16k, 4x4k (128K). Everything leads me to believe this is actually a Macronix MX28F1000P. This correlates with what the datasheet says (attached pdf) where it says the chip is made up of "Four 4-KB blocks and Seven 16-KB blocks". Does anyone know the reason for this unusual arrangement? I suspect it has something to do with what the BIOS refers to as its "NVRAM" when it boots up, but I can find very little reference to what this is for. I was able to try a few different Flash Chips just to get the system to boot, including the Macronix MX28F1000PL. UNIFLASH reports this chip as a much more standard 8x16k (128K chip). While it does work, the system says "No NVRAM" when it boots up but otherwise works normally.

I could not find any Macronix MX28F1000P available for sale, so does anyone know of any substitute parts with that extra 4x4k section that could be used as a replacement? If not, am I giving anything up by using a more normal 8x16k chip and not having the NVRAM available to the bios?