RT-11 DY install

[Pete Turnbull]

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