First post, by Deksor
- Rank
- l33t
Hello !
I've had this board for over two years now, you can see how I got it here : My Motherboard/ISA video/Big old HDD motherlode
After watching necroware's video about fixing the exact same board, I got the motivation to mess with this board again. After having the issue I had before, I just put it to storage.
A bit of history to recap what happened in two years
The board was filthy when I first got it (check first post of my old thread). Then I cleaned it but it was crusty. Then I used the CPU to scrub the socket's pins and I managed to get it to run for some time and it got stuck to "C5".
Then I put it to storage, and it seems that at some point I stole its cache for some other board.
Today I pulled it out of storage and to my surprise I still had POST codes on the POST card. Maybe the socket isn't that finnicky afterall ? First I cleaned it a second time and used some vinegar because I saw some corrosion on the sockets, and it still didn't feel very clean afterall.
I also noticed a burned trace underneath the socket which was cut. So I patched that with a piece of wire. This time I made sure that the jumpers were set accordingly too. Strangely, when setting the jumpers for the FSB (33MHz), the board stopped outputting POST codes. Strange isn't it ? Then I measured the CPU's voltage and I saw "4.0V". This can't be right.
If you saw necroware's video, you know what I did next. I checked the MOSFET and bingo ! The resistance between each pins is really low. So I took the MOSFET out and now it looked normal. The MOSFET had a resistance of 10 ohms between each pins. Next, I stole a MOSFET from a dead slot 1 board and put it in place.
Before installing the CPU I checked the voltage and it was a steady 5V. Nice !
The problem
Next I insterted the CPU and prayed for it to work. And it did !! ... Until it stopped on code C5 AGAIN.
At least I made some progress since the board would never boot on 33MHz setting before, so this is a step in the good direction, but something is still wrong.
The bios is award. According to here, code C5 apparently means "Shadow RAM".
So now the problem seems to be related with RAM ...
This is why I am posting this, I don't really know what to do now. I've tried the usual things : taking the cache out, putting it back, using different memory sticks (I'm pretty sure the one I tried is FPM. But even then, this is one of the rare 486 board that should be capable of running EDO memory), but nothing changes. It always gets stuck on C5.
Only if I take the memory stick off, it will beep at me to signal a memory error (which makes sense). This is also the case if I move the stick in a different slot.
Any ideas on what could be wrong ? This board was also missing many jumpers. I tried my best to add the "factory set" jumpers, but maybe some are missing. Another pair of eyes is better than none for this kind of thing 😁
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