Two of the 74F543's (U14, U23) do seem to be running hotter than the others. Not hot enough to scald but definitely uncomfortable to touch.
Hardware's not my forte; what else should I be looking at as a consequence of the hotter than normal latches? Broken solder joints?
One thing I did notice when I had the motherboard out tonight is that there's something (capacitor?) soldered across a couple CPU pins on the backside of the motherboard... here's a picture: https://i.imgur.com/Z7MUgzb.jpg
Is that normal?
(I straightened out the pins in the top left so they wouldn't come close to touching)
Last post by barcher174 - July 16, 2019, 04:17:50 am
Mine is working. I think in the end it's a different error though. I had an exception #4 which I confused with your error #3. For me the issue was a shorted pin on the ASIC controlling the SCSI controller which was only visible under a scope. I bent it back and reflowed with success. Here's what I would try in your case:
From this we see that the vector number and code match to the table. So it looks like NeXT used this table directly which is good news going forward. The description says:
8.2.2 Address Error Exception An address error exception occurs when the processor attempts to prefetch an instruction from an odd address. This includes the case of a conditional branch instruction with an odd branch offset that is not taken. A prefetch bus cycle is not executed, and the processor begins exception processing after the currently executing instructions have completed. If the completion of these instructions generates another exception, the address error exception is deferred, and the new exception is serviced. After exception processing for the address error exception commences, the sequence is the same as an access fault exception, except that the vector number is 3 and the vector offset in the stack frame refers to the address error vector. The stack frame is generated containing the address of the instruction that caused the address error and the address itself (A0 is cleared). If an address error occurs during the exception processing for a bus error, address error, or reset, a double bus fault occurs.
Last post by barcher174 - July 15, 2019, 06:04:48 am
It seems I have a mono turbo station with the same problem. Recapped, drive swaps, RAM swaps, and cable swaps with no success. I'm convinced there's a board level fault. I'll let you know what I find. The SCSI portion is identical between the color and mono systems.
Last post by barcher174 - July 15, 2019, 03:21:24 am
Cool to see original hardware doing something! If you want to run continuously I would suggest an ATX modification instead of a recap. Firstly because a recap of the station power supplies is a nightmare and secondly because a new power supply is likely both safer and much more energy efficient.