I am also looking for this file I am trying to restore an old 486 with an IH4077 motherboard, I am trying to make it work with a DX4 Overdrive but it won't boot. I'm hoping the new BIOS fixes this issue but I am unable to locate the file anywhere on the internet...
Would someone be kind enough to provide me with he BIOS update file?
Thanks very much
Here you go. Keep in mind that this motherboard does not support BIOS flashing internally, so you need a 27C512 (64kB/512KBits) EE/EPROM with the BIOS flashed onto it. I've done this, and it works fine.
As for the machine not booting, check the jumpers. Jumper settings are here:
http://stason.org/TULARC/pc/motherboard ... 4077D.html
Make sure that JP36 is set to 1-2 (33MHz bus, the CPU has an internal clock multiplier), also make sure that the CPU settings are set to DX2/DX4 (they share the same jumper setting), and that you change the clock multiplier settings on the motherboard as well (prolly 3x (33MHz x 3 = ~100MHz)).
If the CPU requires 3.3v, you need to do a kind of tricky voltage regulator mod. There's a connector next to the CPU with the text "VCC, GND, VCC3, VCC, GND, VCC3". Basically you unplug the big whiter jumper that is in there, and you line up both the VCC and both GND to a 3.3v reg, then you take the 3.3v out and line it up to the two VCC3 lines.
To get 5v mode again, remove your mod and reinsert the white jumper block (or short both VCC with both VCC3. GND can stay open).
The motherboard is sporting a Socket 3 CPU socket, which means that it has the auto-sensing pin for 5v/3.3v selection, but I did a check on this and the motherboard doesn't supply 3.3v, so inserting a DX4 that is 3.3v will result in a 1.7v too much and a PC that freezes after just seconds.
If the system still refuses to boot, bear in mind that this motherboard is kind of picky about RAM sticks, so try other ones. I've had best luck with single-sided RAM sticks.
Also make sure the PSU delivers clean voltage lines within good range. 5v +- 3%, 12v +- 10%, -12v +- 10%.
Hope this helps!