I'm confused. I thought the PMAZ-B `tcds' option card Nisimura-san
mentions *was* effectively the same hardware that shipped on TC Alpha
motherboards, that the TC option is identical (probably pulled from an
Alpha) and the PMAZ-C is a fast-scsi version.

But yes, memory bandwidth may well be a problem, specially if the
Personal DECstation runs its memory bus synchronousy with its
TC/ioctl-asic subsystem.