Cooling a 601 Processor Upgrade card

[philcollins]

Hey y'all,
I recently found an Apple-branded 66Mhz 601 PowerPC upgrade card on eBay that I've installed into my Mystic Color Classic (well, after cleaning off the old thermal paste and applying a fresh coat).

After enabling the device and the new memory manager, I put it through a MacBench benchmark, where it performed admirably, but I've noticed that the machine becomes unstable after about an hour of uptime, whether I'm MacBenching or not. This instability manifests as a full hardlock (though I can at least bring up the interrupt command line when this happens).

I've put the machine through several successive overnight MacBenches in 68k mode and the machine remains rock-solid, so I'm beginning to think that I'm running into an overheating 601. I'm wondering if anyone else here has run into a similar issue or might have any ideas about how to cool one of these beasts.

My current thinking is that I might be able to wedge a chonky Noctua fan right above the processor, perhaps by relocating the CC's internal speaker and tapping into the 12V line that's used for the case fan.

 

[Phipli]

Hey y'all,
I recently found an Apple-branded 66Mhz 601 PowerPC upgrade card on eBay that I've installed into my Mystic Color Classic (well, after cleaning off the old thermal paste and applying a fresh coat).

After enabling the device and the new memory manager, I put it through a MacBench benchmark, where it performed admirably, but I've noticed that the machine becomes unstable after about an hour of uptime, whether I'm MacBenching or not. This instability manifests as a full hardlock (though I can at least bring up the interrupt command line when this happens).

I've put the machine through several successive overnight MacBenches in 68k mode and the machine remains rock-solid, so I'm beginning to think that I'm running into an overheating 601. I'm wondering if anyone else here has run into a similar issue or might have any ideas about how to cool one of these beasts.

My current thinking is that I might be able to wedge a chonky Noctua fan right above the processor, perhaps by relocating the CC's internal speaker and tapping into the 12V line that's used for the case fan.

My first thought would be check that there isn't too much or too little thermal paste. Thermal paste is an insulator designed to be better than air, but not better than metal. If there are air gaps, it is bad, but also, if there is too much thermal paste it is bad.

 

[GRudolf94]

Besides what @Phipli said, is there any documentation on previous success with that configuration? I would be concerned that the 040 board+601 are just too big a strain on the CC PSU, and as things go, it simply sags to the point the machine is unstable. Measuring 5V when the machine hangs would provide some insight.

 

[philcollins]

These are two great points; I ended up repasting the chip, taking care to make sure that the level was right this time, and with it all reseated, the machine seems to be stable in 601 mode! It took 3 MacBenches like a champ, and a measurement of the 5V line under heavy system load was similarly stable, so I think that we're in business.

Thanks much for both of your suggestions, they were quite helpful! I think I might still put a Noctua on the 12V line by taking it from the 4 pin Molex that was used for the hard disk before its replacement with a BlueSCSI, I'll report my findings back to the thread to see if that takes power utilization over the edge.