How do we know that this BIOS is really for the HOT-433 v1-3? I did not see anything in the readme refering to HOT-433. The 1024K may not be detected because you need to set your Alt Bit in TAG SRAM to 8+0 instead of 7+1.
Enabling PS/2 support in the BIOS with ModBin probably won't work on its own. I did some analysis on this a few months back. I'd need to dig through some e-mails to find out exactly what the problem was, but from memory, they did not connect the PS/2 data and clk pins to the proper locations on either the i8042 or the southbridge. I think they tried to gang up the data line for keyboard and PS/2 mouse ports, which will not work on either the i8042 or UM8886 southbridge. v4.0 of the HOT-433 changed their ps/2 pin locations, but they still did not get it right. Some simple PCB rewiring may be all that it takes.
I know on late 1995 and 1996 southbridge UM8886 chipsets, the mouse data goes to pin 199 and clock goes to pin 200. I am not sure if these early 1995 UMC southbridge chipsets had PS/2 support or not. Maybe they do? If they did, you'd need to wire the mouse data/clock to pins 199/200 and add PS/2 voltage and ground. I'd probably try this out with the old HOT-433 BIOS first using MODBIN. FYI, keyboard data/clock goes to UM8886 pins 56/57. I have noted this on the latest version of my Biostar MB8433-UUD manual, which can be found in the World's Fastest 486 link.
Unfortunately, I no longer have time to monkey around with hardware. Best of luck with this!
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