You mean that it should be on the disk in the SIMH s/w kits?, I could not see any source. Its just one rk05 image.
I also read you could get the full source if you asked. -----Original Message----- From: Johnny Billquist <b...@softjar.se> Sent: Monday, July 20, 2020 6:37 PM To: Paul Moore <paulmoore...@hotmail.com>; Simh@trailing-edge.com Subject: Re: [Simh] FW: pdp 11 timing RT11 distribution comes with (uncommented) sources. Johnny On 2020-07-21 00:31, Paul Moore wrote: > At the moment my ambitions are very lightweight. A pdp 11/20 with a cassette > drive (why that? cos CAPS11 is the first sw listed on the simh sw kit page). > And next is an RK11 with rk05. So I can run RT11 (the second thing on that > page). > > The point that I am hearing is that, in general , the PDP11 sw doesn’t rely > on timing , there are a few corner cases tho. Contrast this with other > systems where precise knowledge of video flyback times are built into the > core of the OS for example. Or timing is achieved by looping instruction x n > times to produce an exact delay. > > BTW - does anybody have the source of the RT11 on the simh kit site? I got > the source of CAPS11 from Lou Ernst and it was a life saver. I could not have > progressed without it. > > -----Original Message----- > From: Simh <simh-boun...@trailing-edge.com> On Behalf Of > s...@swabhawat.com > Sent: Monday, July 20, 2020 3:14 PM > To: Simh@trailing-edge.com > Subject: [Simh] FW: pdp 11 timing -->anf10 workstation on pdp11 with > throttling > > > > L.S. > > Actually where this is important, is when using Pdp11 based ANF10 > workstations in the Tops10 realm. > > When starting up, the Anf10 software on the pdp11 sim test various devices > for functionality thereby using instruction count based loops etc. > When all the devices necessary (paper tape reader/punch, incremental plotter > interface, DZ and DH multiplexors, DMS and DUP/KDP devices and DL11 > interfaces) are properly verified, it cranks up the communication > configuration with scanning the network for active Pdp10 Tops10 host systems. > The throttling of the pdp11 should be carefully selected to let this function. > > > Reindert > > > -----Original Message----- > From: Simh [mailto:simh-boun...@trailing-edge.com] On Behalf Of Johnny > Billquist > Sent: Monday, 20 July, 2020 23:20 > To: Paul Moore <paulmoore...@hotmail.com>; simh@trailing-edge.com > Subject: Re: [Simh] pdp 11 timing > > Instruction timing as such is not relevant. Different implementations had > very different timings, not to mention that speed of memory also makes a > difference. > > Devices basically do not have a strict timing either, but yes, there is > plenty of software that assumes that an interrupt does not happen before a > single instruction have been executed after the previous interrupt, from the > same device, for example. > On real hardware that was just an absurd case that lots of code never > considered, since it wasn't really physically possible for it to happen. > > The throttling in simh is because some people want the emulation to somewhat > mimic the real thing. For some people, that experience of slowness is > desirable. > > Johnny > > On 2020-07-20 23:10, Paul Moore wrote: >> (I am writing my own emulator just because I have never done that >> before, and the PDP 11 is such a pivotal system in the history of >> modern computing it seemed worth learning about, and what better way >> to learn than to emulate it ) >> >> So how important is timing of instruction execution and device response? >> >> The PDP 11 docs go to great length giving instruction timing. But >> the fact that there is a % throttle in simh suggest that’s not important. >> I assume that turning that throttle up and down makes the emulated >> CPU go faster and slower. I have seen code using simple counters as >> delays but I assume that if you want precision you use the Kw11. >> >> With regards device responses I have found that going ’too fast’ >> upsets code. If they do something that triggers an interrupt (set ‘go’ >> for >> example) and the interrupt arrives too soon (like before the next >> instruction) they get surprised and can misbehave (you could argue >> that’s a bug, but that’s irrelevant). So always wait a few beats. But >> I assume there is no reason to try to precisely emulate the timing of >> , say, a disk drive. (The early handbooks state how awesome the async >> nature of the IO subsystem is cos you can swap out old for new and >> things just go faster). >> >> >> _______________________________________________ >> Simh mailing list >> Simh@trailing-edge.com >> https://nam10.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmail >> m >> an.trailing-edge.com%2Fmailman%2Flistinfo%2Fsimh&data=02%7C01%7C% >> 7 >> C7737449fd7b940ede41e08d82cfa6bf7%7C84df9e7fe9f640afb435aaaaaaaaaaaa% >> 7 >> C1%7C0%7C637308801343677110&sdata=r%2BGE87iQAYJIJue9GPTrR7FESpVsQ >> m >> hPhKxgm2CZCos%3D&reserved=0 >> > -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: b...@softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol _______________________________________________ Simh mailing list Simh@trailing-edge.com http://mailman.trailing-edge.com/mailman/listinfo/simh
