Unfortunately, it only runs about 15 minutes and then crashes. 
But, that's not too bad for a chip that's only marked 33Mhz. That's a nearly 50% overclock!
I used some tiny heatsinks on the cache chips and a GeForce 4 heatsink on the 68040. Now I'm just waiting for that 40Mhz part to get here...
You'll easily get there with a 40MHz!
If I want to add an FPU to a PowerCache, does it have to be the same speed rating as the CPU? For example, if I have a 50MHz 68030, can I use a 40MHz 68882? Does anyone know a good source (machine to part out or store) for 40-50MHz FPUs?
On a related note, I was corresponding with the guy from Artmix since he just had an eBay auction for his infamous adapter and a PowerCache (for $200), and he said it was a 40MHz CPU running at 50MHz. I then asked if it was safe to OC a 33MHz 030 CPU to 50MHz without a heatsink, and he said it was ok. I know 030 and 040 are not the same, but after seeing these results, I kind of doubt it.
The question is what format you need them to be. Does the PowerCache have a socket for a PGA 68882 or for a QFP one? If it's PGA, I'd look in old HP servers and dead IIfxes. If it's QFP, I think you might be kinda screwed.
The speed doesn't have to be the same, but it'll be RUN at the same speed. I bet if you put a little hotsink on it you could run a 40Mhz 882 at 50Mhz.
It's a lot more likely than to run a 33Mhz 040 at 50Mhz without a heatsink.
The 50Mhz PowerCache boards I've sold all had genuine 50Mhz 68030s and 68882s and no heatsinks whatsoever. Ever seen a 40Mhz 68040 with no heatsink? The 68040s run a lot hotter.
I'm sure it's "safe" to try overclocking a 33Mhz 68030 to 50Mhz without a heatsink, I doubt it could get itself hot enough to cause damage. But, you might not have the greatest stability. I'd go get a northbridge heatsink out of an old dead PC at the very least.
Have you tried installing a fan on your heatsink? That might help things out if it's a heat issue. Otherwise, your CPU just may not be able to handle the increased speed.
Cheers,
The Czar
Oh, yeah. I've been running a GeForce 4 Ti heatsink with lots of little fins and a tiny fan that runs at some huge RPM.
I got an 840AV and swapped CPUs. Now the 40Mhz chip is running at 48 stably in my SE/30 and the 33Mhz chip runs at 40Mhz stably in the 840. Perfect!
I do think I could have gotten the 33Mhz chip to run stably at 48 if I had a *really good* heatsink, but there's just not room for it.