11

I'm curious if anyone is aware of actual uses of Unix on the Heathkit H11? I don't see any technical reason a memory-expanded H11 couldn't run Unix, but can't find any examples of it doing so.

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    Plausible. The H11 is an LSI-11/02 with max 32 kW of memory, and Unix "V6 will run on an LSI-11/02 with 28KW of memory." mail-archive.com/cctalk@classiccmp.org/msg44100.html – snips-n-snails Oct 16 '19 at 20:16
  • Nice question. Can't provide an Answer. Still, AFAICT, it should work. The H11 was basically a PDP 11/40, while the H11A is the equivalent of a 11/02, and could use any Q-Bus interface, including disks. Heath themself supplied an RX01 alike floppy and a RT11 version. So loading (some) Unix might work quite well - given a disk controller (Q-Bus SCSI or alike) is added. – Raffzahn Oct 16 '19 at 20:16
  • Did these CPUs lack supervisor mode? and if so, did Unix need it? – Maury Markowitz Oct 16 '19 at 20:54
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    An LSI-11 has an 11/40-ish instruction set but it doesn't have an MMU, so it's a single-mode single-space processor. That limits the operating systems you might run. From dusty memory cells, also, the PS is not accessible through the IO page (like normal -11 CPUs), but only via a new instruction, so it's likely not even binary compatible with unmapped operating systems. – another-dave Oct 17 '19 at 0:38
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    @ralfzahn - careful with that "11/02". Generally speaking, "11/xx" means "PDP-11/xx", and there's no such thing as a PDP-11/02. There's also an "LSI-11", which is the microprocessor and/or the CPU module used in the PDP-11/03, and an LSI-11/2, no zero, which is its replacement (same microprocessor, different CPU module). Ain't DEC nomenclature grand? As far as I can tell from the 'net, the H11 was based on the LSI-11 board, and the H11A was based on the LSI-11/2 board. They're both 16-bit bus devices. – another-dave Oct 17 '19 at 1:44

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