Alphaserver 1000 diagnosis?

(I think I asked this once before, but I can't remember the result and I can't find the thread in the archive) I have an Alphaserver 1000 that I would like to resurrect. It periodically hangs or reboots. When it reboots the error is usually "Machine check while in palcode". When it hangs, the hang is so severe the halt button does not work. Either way, it always happens within 20 minutes of booting. I ran all of the diagnostics you get by moving the CPU card jumper (cache memory tests, RAM tests) and they run for an hour or so with no error. (I am assuming the diagnostic halts on error instead of just looping again, is that correct?) During the course of these I moved the jumper to the wrong place and wiped out SRM, so I had to reload SRM from floppy using the failsafe loader. That worked. The SRM diagnostics will also run for as long as I want without error. Does anyone have any idea what's wrong here or is there some kind of XXDP-like thing I can run that will better test the machine?