WTB: SGI Professional IRIS CPU / Help Needed

Hi there, I'm owner of a Professional IRIS 4D/50G made by Silicon Graphics some time around 1987. The machine has apparently some kind of trouble related to the CPU board. I'll include some details further below, I'm open to any good idea. Because of that problem I'm in search for a suitable CPU board. The failing board is a IP4 CPU board (part nr. 030-0121-001 Rev A). I presume that any kind of CPU board from a Professional IRIS line machine would help (mainly IP4 and IP4.5). Please drop me a note if you have a spare or can point me in a promising direction. As promised some details. The machine used to work fine once I had set it up quite a while ago. Recently it refused to boot and upon inspection I got the following error: ---- snip ---- EXCEPTION: <vector=NORMAL> Exception pc: 0xbfc108a0 Cause register: 0x30001008<CE=3,IP5,EXC=RMISS> Status register: 0x80000<CM,IPL=8> Bad Vaddress: 0xc0000000 Error Addr register: 0x17b40 Local I/O interrupt register: 0xff <> Parity error register: 0x0 Registers (in hex): arg: c98cf600 ffffffff 15180 0 tmp: 0 0 0 0 0 0 0 0 sve: a0017b93 bfc268c8 bfc268ca 1 54 0 1 800 t8 ff00 t9 502e8000 at 1 v0 c0000000 v1 f65da k1 bfc04234 gp 0 fp bfc04bd0 sp a0017b64 ra bfc10744 exit(-1) called ---- snip ---- This happens just after POST (I think) when the machine is either about to start IRIX or to show the PROM menu. Of course nothing further happens except that the error is repeated without end. I did strip the machine down to a bare minimum of boards (IP4 and Ethernet) and I also swapped the memory sticks. The only things I could reasonably pull in a last attempt would be the VME Ethernet board and the system disk. Regards, Gerhard -- http://www,sgistuff.net/