18 Oct
2018
18 Oct
'18
9:29 a.m.
On 18/10/2018 13:22, Don Stalkowski via cctalk wrote:
On Wed Oct 17 19:19:20 2018 cctalk at classiccmp.org
(Jerry Weiss via
cctalk) wrote:
> Note: Apparently the RY emulation won't load
if more than 256K
> memory is specified as the DEC hardware did not support DMA in a
> 22bit box. I'm=20 entirely not sure why SIMH has to
> enforce this as its possible to work around (e.g. TSX+ supports
> buffering the IO). Anyone know how to override and load in
> SIMH?
>
> Jerry
Thanks Jerry. That's "fixed" it. Since
simh didn't complain about my
"set ry enabled" I assumed (wrongly) that that wasn't the issue.
Thanks to all the other's who replied.
As Noel pointed out, real PDP-11s definitely work with RX02 subsystems
in 22-bit systems. SIMH really ought to be able to do so regardless of
18-bit or 22-bit memory. The DY driver in RT-11, for example, simply
knows to only use the bottom 256K for DMA I/O.
--
Pete
Pete Turnbull