Hi B24Fox,
I did the comparison between the 1st and 2nd original M577 BIOS. The result: they are byte for byte identical!
So unfortunately no clues for the performance issue on the 2nd board here. 🙁
The reason you see a different checksum is that off course the ESCD blocks are different. This 4KB block is where the BIOS stores its Plug&Play data, and is located at offsets 1D000h-1DFFFh in this BIOS file.
Only if you would have used the exact same set of expansion cards and peripherals on both boards, the ESCD blocks would have been the same.
The CMOS memory of only 128 bytes, used for the RTC registers and the BIOS Setup menu selections, is much too small to house the PnP resource assignments. So a dedicated 4096 bytes block in the BIOS flashchip is used to store this so called Extended System Configuration Data.
So when doing a (binary) compare of two BIOS files, always disregard differences in the ESCD block.
As a sidenote, the BIOS will check the PnP data during each boot-up and update the ESCD block when a hardware change is detected, even if you just placed the graphics card in the next PCI-slot. You can observe this process via the BIOS message “Updating ESCD…….Success” at the end of POST on the BIOS summary screen.
However, if you suspect that old PnP data is not cleared correctly and can be responsible for resource conflicts, you can manually clear the ESCD and let the BIOS load a fresh set of PnP data, by Enabling the “Reset Configuration Data” BIOS option.
This is a one-time action. On the next boot, “Reset Configuration Data” will be Disabled again.
Cheers, Jan