[Simh] Simulating the PDP-15/76 Unichannel

[Johnny Billquist]

On 2015-03-19 04:21, Timothe Litt wrote:
> On 18-Mar-15 20:34, Rich Alderson wrote:
>> [1] Developed mostly from RSX-11M, with a few nods to RSX-11D, at
>>      least as far as the doc writers were concerned.
> -11M, but -11D device drivers and a heavy dependence on event flags.
> No memory mapping; it was a stripped-down environment.
> 1 RP04/6 disk dual ported; the 11 driver had to deal with 18-bit (576 byte)
> formatted sectors.
> The queued protocol provided access to unibus peripherals, including
> async lines, card reader, LPT and (my secret contribution, a
> battery-backed-up
> TOY).  This wasn't pure pass-thru; the 11 did a lot of the low-level
> control and
> presented abstracted devices.

This is getting rather far off-topic, but anyway...
Do you have any source for the claim about -11M with -11D device 
drivers? As far as I know, one of the major differences between -11M and 
-11D is just the device drivers, as the whole I/O subsystem was 
redesigned in -11M, for a smaller memory footprint and better efficiency.
-11D could not run without an MMU, while -11M can. Thus it sounds 
strange that you'd have -11M with -11D device drivers. I would suspect 
that would be impossible, and in addition the -11D device drivers would 
require more resources than their -11M counterparts, which would be 
rather opposite of what was required of the 11/40 FE, which is rather 
limited on resources.

My recollection of RSX-20F is that it very much feels like an unmapped 
-11M system. Some changes because of the special requirements, but 
nothing major.

	Johnny