On 2013-01-06 21:22, Paul_Koning at Dell.com wrote: On Jan 6, 2013, at 2:50 PM, Johnny Billquist wrote: ... I'm even more curious what a PDT-11 optimization is doing in an RSX driver...was there at one time an RSX product product planned for the PDT family? I'm not at all surprised to learn that RSX ran on the PDT-11. RSX can run on pretty much any PDP-11, as long as you have atleast around 50K of ram. That's about the lower limit, I'd guess. No other hardware frills or features required RT requires far less. In college, I ported RT to run on the physics department 11/20, which had 8 kW of memory. It required a port because for a disk it had an RC11, which RT did not support. Fortunately, one of the RT authors had come to work at our college, and he helped me a lot. I asked him "why no RC11 support". Answer: "there weren't any around DEC to test it on". Yes. RT-11 can run on even smaller things, but RSX can really run on much less than most people believe. Originally that machine ran DOS-11 V4, ugh. RT was a much better OS. We ran RT Basic on it, with mods I made to support all the lab equipment (DR11-A, AD-01, AD-11, KW11-P). Interrupt handlers written in Basic, fun... BTW, does anyone know why SIMH doesn't support booting from RC11? Noone have written the code for it? :-) Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt at softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol