22 Nov
2019
22 Nov
'19
2:05 p.m.
On Fri, Nov 22, 2019 at 6:39 AM Noel Chiappa via cctalk <
cctalk at classiccmp.org> wrote:
So I think all our questions are answerered (except
for the [RH11]-AB/-C
difference
issue).
One version of the RH11 added a small FIFO (called a "silo" by DEC, IIRC)
in the data path. I don't recall which suffix that was, nor whether it was
the version used in the KS10.
Presumably the reason for the FIFO would be to help disks work reliably on
relatively "low-end" systems that can't wire the RH11's Unibus B to
dual-ported memory. Since the KS10 has separate UBAs for the disks and
tape, I wouldn't expect it to need the FIFO version of the RH11 unless
there were problems with latency arbitrating for the KS10 bus. I would
imagine that DEC gave the UBAs priority over the CPU.