Yes I did that test, and the CPU too.
I have two Wallstreet PDQs:
1) Apple 266MHz G3 CPU with 128MB RAM and 40GB internal HD
2) Sonnet 500MHz G4 CPU with 512MB RAM (8 chips per 256MB RAM card) and 80GB internal HD
The Wallstreet with the 500MHz Sonnet card has the crashing problem. So I yanked that CPU (leaving the 512MB RAM connected) and then insert it into my other Wallstreet which has Apple 266MHz G3 CPU card (with 128MB RAM connected). (I was able to do this without any Sonnet CPU card firmware conflicts because both my Wallstreets are PDQ models with the same exact ROM.) I put the machine back together again, including the heatshield, then booted. The Wallstreet then booted right away (faster, of course) and I have been running disk, RAM and CPU intensive benchmarks for about 15 minutes now, without even a single crash at all. That is long enough to heat up the CPU, so if heat was a problem on the other Wallstreet, it certainly is not on this Wallstreet.
So my test confirms two things:
1) The Sonnet CPU is fine
2) Each of the 256MB RAM cards attached to the Sonnet CPU are fine
Therefore, why would my other Wallstreet be crashing so consistently?
Thanks.