512K, Sad Macs 0F000A and 05FFFF

[Random73]

Hope someone can help regarding one of my Mac 512Ks;

When cold, my Mac 512K powers up, boots from disk, and runs perfectly fine for up to a few minutes, then it freezes or Sad Mac 0F000A comes up. After a power off- power on cycle, it comes up immediately with Sad Mac 05FFFF.

If I cold start it and simply do nothing except watch the boot screen, this same Sad Mac behavior occurs after as many as 8 to 10 minutes of normal boot screen.

If I wait long enough, such as a day or two, these behaviors always repeat.

There doesn't seem to be much info available about these failures. It is easy to look up that 0F is "software exception" and that 000A is a "Line 1111 error". Does anyone have useful information as to what is line 1111?

Similarly, 05 is memory test-"address uniqueness" fail and and FFFF blames all sixteen DRAMs. Can anyone provide more in-depth what is "address uniqueness"?

I have done the usual first steps; voltage regulator check, re-seat the ROMs, visual board inspection, etc. to no avail. I thought about trying freeze-spray, but I have no experience with it, and don't know what the risks might be, if any, or which parts to try it on first.

Any suggestions/advice would be most appreciated, thanks

-73

 

[olePigeon]

My first suggestion is always to recap the motherboard. The 512k doesn't have very man capacitors, so it should be a quick job.

In any event, sounds like something is heating up and a trace is being broken. I wouldn't know where to start.

 

[mwillegal]

address uniqueness means that each physical memory address uniquely addresses a different memory cell. A failure means that multiple addresses targeted the same cell. Example - address 1000 and address 3000 both touch the exact same memory cell. This essentially means that memory test found a discrepancy in memory addressing. Since all chips are affected, it's probably not a memory chip issue, but a processor or addressing logic issue.

It's hard to troubleshoot intermittant issues like this, but checking the power supply voltages is a good idea.

regards,
Mike Willegal