Hi list,
  I have a question for those of you who have fast CMD/DILOG Q22 SCSI
controllers. Do you have trouble to run NetBSD 1.5.2 (maybe other
1.5.x too) on your Qbus VAX with CQBIC CDAL-Q22 controller? I found
that if my board performed two burst mode DMA transactions in one DMA
grant, the machine had machine check 10 errors (10us time out when CPU
accessed memory that was mapped to the QBUS) from time to time. If I
set the board to have one transaction a grant, there was no machine
check 10 error. I read the diagram carefully and it seemed my board
followed QBUS DMA protocal well. It was the CQBIC controller that
prolonged the DMA (slow RPLY as response to DIN).
  I guess there are two solutions. One is that the software re-try the
memory after machine check and keep going. The other is to stay with
single shot DMA and be very slow. My guess is those fast CMD/DILOG
boards have this problem with CQBIC too. If so, VMS would take the
re-try approach. Could you conform or deny my guess? Thank you.
  My system is KA655 + two MS650-BA. Thank you.

vax, 9000