On 18/10/2018 13:22, Don Stalkowski via cctalk wrote:
On Wed Oct 17 19:19:20 2018 [email protected] (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
