
PDP2011: A re-creation of the PDP-11 computer systems in VHDL - ljosa
http://pdp2011.sytse.net/wordpress/pdp-11/
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bcaa7f3a8bbc
DEC actually made a microprocessor implementation of the PDP-11 processor,
called LSI-11. It has two chips, and is functionality equivalent to the large
thing. Unfortunately, DEC was in a complete disregard of personal computers or
workstations at that time, I don't think they made workstations with it.
Otherwise it could be another legend in computing history: a PDP-11
workstation! Never happened.

Here's S100 computer board built around this microprocessor with a great
introduction to the hardware details.
[http://s100computers.com/My%20System%20Pages/PDP11%20Board/P...](http://s100computers.com/My%20System%20Pages/PDP11%20Board/PDP11%20Board.htm)

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WalterBright
I had an LSI-11, in the Heathkit H-11 configuration. A wonderful machine. It's
my background picture here:

[https://twitter.com/WalterBright](https://twitter.com/WalterBright)

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kurtisc
(In)famous for being 'middle-endian'

[https://en.wikipedia.org/wiki/Endianness#Middle-
endian](https://en.wikipedia.org/wiki/Endianness#Middle-endian)

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jhallenworld
I used RSX-11M and I remember a few interesting things about it. First, it had
an overlay linker: code would swap in if it used the same space as other
unused code. Second, this extended to the operating system. There was a giant
system build process where you linked all system programs in with the
operating system. To run a command, it first had to be explicitly loaded into
memory. So during this system generation process, you decide which commands
should not interfere with other commands so that many could be loaded at once.
Anyway, I remember it took many hours to run this process.

The 'M' means the system had virtual memory, but virtual address space was
tiny- smaller than the physical memory space.

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cptnapalm
Johnny Billquist wrote a TCP/IP stack for RSX a few years ago and a webserver
too. [http://magica.update.uu.se/](http://magica.update.uu.se/)

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cbm-vic-20
I'm so happy to see an upswing in PDP-11 projects in the past year. It's such
a nice architecture- very extensively documented, and from a time where it was
possible for a programmer to really understand what the machine is doing, top-
to-bottom.

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ChicagoDave
Another rathole to chase down. If I could emulate an 11/70 but connect a real
decwriter paper terminal, I’d be doomed.

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cbm-vic-20
You can use SimH for the emulation, which can direct emulated serial port to a
physical one on your host. If your DECwriter has the EIA/RS-232 option, you're
in business.

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drfuchs
Weren’t all DECwriters, and just about any terminal from the 1970’s on, pretty
much exclusively RS-232?

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cbm-vic-20
A lot of serial equipment back then still had 20mA current loop. For example,
the ASR 33 Teletype[1], which was often connected to PDPs of its era did not
have RS-232.

[1]
[https://en.wikipedia.org/wiki/Teletype_Model_33#Communicatio...](https://en.wikipedia.org/wiki/Teletype_Model_33#Communications_Interface)

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jascii
Easily fixed with an opto-coupler, a transistor, and a hand full of
resistors..

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cptnapalm
There is another VHDL PDP-11 called the W11a:
[https://wfjm.github.io/home/w11/](https://wfjm.github.io/home/w11/)

One eventual goal is for it to be a PDP-11/70mP, a PDP-11 "quadcore".

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ncmncm
BSD 2.x is tbe most insane OS ever. It is a backport from Vax Unix 4.x --
which used real virtual memory, often "lots" of it (2MB or even more!), 32-bit
registers -- back to the 16-bit PDP-11, which had two (count 'em) 8Kbyte
mappable pages in its 64K address range, and could swap 8 other pages into
each. It came with all the same utilities as Vax Unix, except the networking
bits.

We were so happy when we got a big -- 3" high, 6-platter 5.25" 20M -- Shugart
disk. Didn't know we needed to recompile the kernel so it wouldn't swap in the
middle of the fs (which had been at one end of the old 5M disk).

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cptnapalm
2.11 BSD is still maintained by Steve Schultz. Latest patch level is 451
released last year.

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wickedcooldog
This is really cool, though I have never played with the PDP-11 architecture.
When I first took computer organization and architecture at my alma mater,
Wittenberg University, my computer science professor (Brian Shelburne) made us
learn the PDP-8 architecture. I will never forget learning machine code on the
PDP-8. He was very popular among the PDP-8 fan community as he developed two
different emulators for the PDP-8 and published a few articles on using the
PDP-8 in teaching computer science. He made an emulator for Windows DOS and
later on a different one in C++ for Windows 7/8/10.

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jascii
I'm so drooling at the idea of building a pdp-11 laptop right now!

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tyingq
Supposedly, this project was going to include pinouts for the mini-replica
front fascia provided by Pidp-11...a pretty cool project itself:
[https://obsolescence.wixsite.com/obsolescence/pidp-11](https://obsolescence.wixsite.com/obsolescence/pidp-11)

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DerekL
Cool! Now let's make a FPGA clone of _Super Sprint_.

[https://en.wikipedia.org/wiki/Atari_System](https://en.wikipedia.org/wiki/Atari_System)

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FerretFred
I can't get onto this site - just times out - anyone else ?

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shakna
Yep. But thankfully archive.org has it. [0]

[0]
[https://web.archive.org/web/20190708094632/http://pdp2011.sy...](https://web.archive.org/web/20190708094632/http://pdp2011.sytse.net/wordpress/pdp-11/)

