Machine check, type 0 (VAX 780)

[P McFerrin]

> Does anyone know what 'Machine check, type 0' is on a VAX 780?
> The message also says 'CP read timeout fault' and prints some
> registers, but I can't find any documentation around here that
> describes things like that. We have goten four of them since
> last Wed.
> 
> We are running 5.2.2 with 4M, one rm03 and one rp07.
> -- 
> 
> Alan Fargusson.
> 
> { ihnp4, amdahl, mot }!drivax!alan

This problem is caused by a device on the Unibus.
It occurrs when a device fails to reply with its vector address when requested
so during a bus-request/bus-grant protocol.  This can be a tough problem
to isolate.  I know of no proceedure to find the culprit except by
replacing one board at a time.

Another cause of this problem can be external wiring to a DR-11 interface
(parallel i/o).  Noise on the request A or B lines can cause the DR11
to withdraw in the middle of a bus-request/bus-grant protocol.

It is a hardware problem.