Re:Building the PiDP-11 Dec PDP-11 Replica Minicomputer
by zh3 on Wednesday November 23, 2022 @03:23PM
(#33724064)
800MIPS? Not off an 11/70, for sure - much, much slower than that. 11/23's were as fast (or faster, depending on options and application) and they were maybe a single MIP or so (still got a couple of PDP11's kicking about, every so often I fire them up just to check my hearing).
Re:Building the PiDP-11 Dec PDP-11 Replica Minicomputer
by bdavis__ on Wednesday November 23, 2022 @03:27PM
(#33724102)
From memory.
(The original) VAX 11/780 was a 1 MIPS machine. 32 Bit.
pdp 11 was a slower machine. plus it was 16 bit. slow clock, a relatively cheap o'scope could be used to snoop the buses.
Re:Building the PiDP-11 Dec PDP-11 Replica Minicomputer
by timonoko on Wednesday November 23, 2022 @03:41PM
(#33724256)
50 cent EPS-8266 would make excellent PDP-11. Except much too much memory. And 20 times too fast.
Re:Building the PiDP-11 Dec PDP-11 Replica Minicomputer
by zh3 on Wednesday November 23, 2022 @03:35PM
(#33724189)
Indeed, back in the day we bolted QBus backplanes to the side of DIN41612 backplanes and wire-wrapped across to a bunch of boards each with 100+ TTL chips on them (the 5V PSUs were something like 120A). The bus clocked at around a MHz, hence loosely the instruction rate (and back then, the addressed memory or peripheral needed to ack the bus cycle or there'd be a bus fault).
Re:Building the PiDP-11 Dec PDP-11 Replica Minicomputer
by williamDafoe on Wednesday November 23, 2022 @05:04PM
(#33725108)
The original PDP-11/70 was 0.7 vax mips. So it was 70% as fast as a Vax 11/780. I believe (from memory) the Vax 11/780 could do ~1757 dhrystone 2.1 mips so a PDP-11/70 would be about 1230 dhrystone mips.
https://wiki.cdot.senecacollege.ca/wiki/Dhrystone_howto
The Raspberry PI3 is rated 2,411MIPS.
This emulator must be much faster than the original PDP11 even with the emulation software.