17 Jun
2018
17 Jun
'18
4:57 a.m.
From: Johnny Billquist
incidentally have 18 data bits, but that is mostly
ignored by all
systems. I believe the KS-10 made use of that, though. And maybe the
PDP-15.
The 18-bit data thing is a total kludge; they recycled the two bus parity
lines as data lines.
The first device that I know of that used it is the RK11-E:
http://gunkies.org/wiki/RK11_disk_controller#RK11-E
which is the same cards as the RK11-D, with a jumper set for 18-bit operation,
and a different clock crystal. The other UNIBUS interface that could do this
was the RH11 MASSBUS controller. Both were originally done for the PDP-15;
they were used with the UC15 Unichannel.
The KS10:
http://gunkies.org/wiki/KS10
wound up using the 18-bit RH11 hack, but that was many years later.
Noel