Well I've now tried some other SCSI CD-ROM's on my VAX, and they all get
the same error. N.B. they all work fine with OpenBSD 5.0 on hppa, alpha,
and i386. So after some more diffing around I found the driver for the NCR
54C94, and the error message I've been seeing.
* The DMA operation was started for
* a DATA transfer. Print a diagnostic
* if the DMA counter and TC bit
* appear to be out of sync.
printf("%s: !TC on DATA XFER"
" [intr %x, stat %x, step %d]"
" prevphase %x, resid %x\n",