VOGONS


First post, by nezoc57

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Hi guys!

I got a 486 board a while ago, an Epox GXA486SG Rev 0.0 (https://theretroweb.com/motherboards/s/epox-pronix-gxa486sg), has a SIS 471 chipset. Seems to be nice, but unfortunately the cache was very fake.

So, i removed the fake chips and added sockets... yet still it doesn't seem to detect anything. I have done the same for a PCChips M912 board, that just worked after replacing the cache chips. Looking into it, my board looks exactly like this picture from TRW, which also seems to have soldered fake cache.

kdn1401-02c-front-61236c974f630217190252.jpeg

There's also a pic of a version with real cache, or at least DIP sockets for it.

img-20230414-221320-644248f06f06a478069162.jpg

Notice that this one seems to have more jumpers populated, and a couple of 74F244 ICs which are not present on the fake cache version. So, i added those ICs and jumpers, configured them properly and.... still nothing 🙁
Then i checked with a multimeter if the cache lines were going anywhere. they seemed to, and data/address lines seem to go to the chipset (or one of those ICs i just soldered), BUT VCC and GND don't seem to be connected to anything. they measure 0v... so i tried hooking them up to 5V, and still nothing.

Has anyone had any luck with these boards? Or maybe with another SIS 471 board with fake cache. Always thought this fake cache scam was a PCChips thing, guess it was far more common than i thought 🤣. At least i'm practicing my desoldering 😜

Reply 1 of 3, by majestyk

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I have quite the same board (KDN-1402C, with cache and voltage regulator) and "J9" at the cache sockets has a bridging wire 2-3 soldered in.

Reply 2 of 3, by nezoc57

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majestyk wrote on 2025-01-15, 13:15:

I have quite the same board (KDN-1402C, with cache and voltage regulator) and "J9" at the cache sockets has a bridging wire 2-3 soldered in.

thanks for the suggestion! it didnt seem to work sadly. i wonder what that jumper does? it doesnt seem to be documented, but probing with a multimeter some traces seem to go to one of the 74F244s, so it's definetly related to cache. also tried to flash a different bios and it doesn't make any difference either.

i wonder if my 244s are bad though. i did pull those from dead boards after all, so i'll order some and give it a try. will update here if i have any luck.

Reply 3 of 3, by majestyk

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Here´s the best (AWARD) BIOS I found for this mainboard:

The attachment EPox-GXA486SG-Rev-J.1-BIOS.zip is no longer available

It supports all the DX4 CPUs.