Chkcpu wrote on 2022-05-02, 20:39:

I did a detailed analysis of the 4DUV VER 3.1 BIOS and I couldn’t find any omissions or bugs in the DX4 support. It is all the […]
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DaveDoc1984 wrote on 2022-04-28, 10:02:

Thanks Jan, if you could check to see if it supports DX4 (which the motherboard I have suggests it should do) that would be great. I will sort myself out with a Compatible EEPROM so I can burn it to a chip to test.

I did a detailed analysis of the 4DUV VER 3.1 BIOS and I couldn’t find any omissions or bugs in the DX4 support. It is all there, just like in many other late 1994 BIOSes.

Because all L2 cache and DRAM timing options in the CHIPSET FEATURES SETUP menu were hidden and operated on automatic only, I restored them so you now have manual control over these settings.
While I was at it, I fixed the Year 2094 bug, the 2GB HDD size display limit bug, and added Am5x86-133 support as well. 😉

Here is a copy of this “patch J.2” BIOS to play with. I hope this helps with your DX4 problems.

Cheers, Jan

Hi, sorry to resurrect such an old thread (of mine). Is there a BIOS Flashing Utility I can use to flash this to the original BIOS Chip OR do I have to use an external programmer?

I have tried various AWDFLASH versions and none of them seem to work.

Hi DaveDoc1984,

I know only of a few late 486 PCI boards that had a Flash EEPROM chip and could use a Flashing Utility, but all other 486's like your MD-4DUV need an external programmer to program the BIOS chip.
Your original BIOS chip is probably a 27C512 or equivalent UV-EPROM. These chips need to be erased by UV-light, hence the quarts window on top, before you can re program them.
So it is much easier to buy a new (E)EPROM to program the updated BIOS and keep the original EPROM as backup.

I agree with TheMobRules's advice earlier in this thread to use a W27C512 EEPROM. These are compatible with 27C512 UV-EPROMs but can be electrically ereased for re-programming. No hassle with UV-light anymore. 😉

Jan