Here’s another update and I should have nearly everything sorted out now:
1) I had a failing motherboard to begin with. It is dead now. I believe the board was tired and had seen nearly 6 or 7 years of continuous use. A powersupply attached to it had failed over a year ago possibly sending a deadly voltage spike through the board when a capacitor inside exploded. The board continued to work afterwards and the incident was forgotten.
I was able to acquire a brand new OEM replacement board to continue testing the K6-2+ 450 and the patched BIOS. It made sense to get this board after acquiring the 50ns EDO. I had debated on getting a Super7 board but that would have required PC100 that I didn't have.
2)My original board came with a NEC/Packard Bell BIOS that I believe had the bootblock write-protected. Although the patched BIOS flashed successfully, I don't think all the BIOS settings were fully functional. Primarily some of the memory timings that were unhidden did not work.
The new board I acquired had a very early Packard Bell version 1.00 BIOS that was not write protected. The patched BIOS was able to completely overwrite this early Packard Bell BIOS making all BIOS settings fully functional. I was able to hot flash the old BIOS chip, which I keep as a spare.
3)The Clear CMOS jumper didn't work properly on either board. I've found that to properly clear the CMOS I needed to also remove the battery and disconnect the power from the motherboard in addition to moving the Clear CMOS jumper for maybe 10 minutes.
4)The ACPI IRQ routing bug that I experienced is not present in the patched BIOS after all. This bug appears to have been carried over from the former BIOS possibly due to the inability to overwrite the bootblock. In fact, the patched BIOS doesn't even appear to implement ACPI which I don't have any problem with.
5)The patched BIOS still reports my hardrive as UDMA-5 even with the 40-wire IDE cable but it operates completely stable after switching cables with UDMA enabled.
6)The new board still doesn't like to run the L3 or external cache at the 66 or 75 FSB with the K6-2+ but after some testing I've found this board is significantly faster with the K6-2+ even without the motherboards cache enabled. Performance seems to be on par with a Super7 board. 400(6x66) seems to be the most stable clock for this K6-2+ 450 and this motherboard. Maybe a different CPU would perform better than the one I have. I thought about trying a low voltage K6-IIIE or underclocking a K6-2+ 533 to see if they would run at 450 more stable.
I’ve also tried a regular K6-2 at 450(6x75) with this patched BIOS and it performs very well with the tightest memory timings.
I'm a little suspicious of the CPU voltages put out by this board. I think this board may be overvolting but I can't be sure. I'm considering getting the Processor Protector here:
or just testing the CPU socket with DVOM to confirm the voltages.
7)I’ve also been testing Windows XP with SP2 on this board and they work fine together. I just needed to download the newer SiS XP UDMA IDE204a drivers to be able to enable UDMA2 for the IDE controllers.
There appears to be an even newer Packard Bell BIOS available for this motherboard than I previously thought. It is version 1.09 dated 11/15/1999 and appears to have hardrives supported up to 65GB. It lacks the memory settings available in the patched BIOS unfortunately and still doesn’t support Write Allocation.
It can be downloaded here if anyone is interested:
http://members.driverguide.com/driver/d ... rid=117568
I believe this was the last BIOS ever put out for this board by anyone. I’d be interested to know if there was another newer BIOS out there.
I'm going to park this machine where it's at for now and may try testing some more things out with it at a later time.