29 Dec
2008
29 Dec
'08
5:45 p.m.
Subject: T-11 (was Re: PDP-11/70 cache memory)
From: "Ethan Dicks" <ethan.dicks at gmail.com>
Date: Mon, 29 Dec 2008 19:21:07 -0500
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
On Mon, Dec 29, 2008 at 5:52 PM, Gordon JC Pearce MM3YEQ
<gordonjcp at gjcp.net> wrote:
I have a few T-11s and they are fun to play with. The bare T11 will
run RT-11 without mmu. The real problem is you need DL serial (or fake it)
and also a disk otherwise you have to build your own drivers.
The VT24x terminals used it and they actually implmented the basic
PDP11 MMU to get 18 bit addressing. the parts load to do that is
not steep but it didn't have the memory protection half of the MMU.
Alexandre Souza wrote:
> The SBC6120 is a **real nice** SBC...
Yes it is, and it's back in "print"!
... [I] wish I had saved a T-11 (was it?)
> processor from many of the arcade boards I saw going to trash...I do not
> even know how to operate a PDP, but it would be something fun to learn :o)
T-11s aren't terribly rare. Perhaps not as common as other 40-pin
CPUs from the 1980s but they can be found on DEC boards and in at
least one DEC terminal. The issue of using one in a modern
SBC6120-like board has been brought up from time to time, and one of
the limitations I think I recall is that they don't have a MMU and,
unlike the F-11, there wasn't one for it, severely limiting your OS
choices. Between that and it not being simple to emulate DEC
interfaces down to the CSR level, turning a T-11 into a bootable
PDP-11 isn't easy at all. Making a 64KB board that runs PDP-11
instructions isn't hard - but then what do you do for software? It's
a harder problem to solve than on the PDP-8 since there really is only
one dominant OS there (plus a lot of OS-less paper-tape software).
Writing _a_ disk driver for one OS for your new disk (such as with the
SBC6120) isn't a terrible obstacle. For the PDP-11, you have to
consider that folks would be interested in RT-11, RSX, RSTS, and
several varieties of UNIX.
The T-11 would make a fun little board if you happen to
know or want
to learn the PDP-11 instruction set and have a use in mind for some
configuration smaller than a console line and a disk/disk emulator.
In this day and age a disk would best be a SD or maybe CF part fewer parts
and easier to bring up.
I think I
asked the question a couple of years ago, about which "classic"
non-typical CPUs turned up in arcade machines. I seem to recall someone
saying that the T-11 was used in Paperboy.
Yeah... I remember reading about the T-11 in Paperboy some time back
and was quite surprised. Large quantities of video games spanned the
progression over the years from 8080 to Z-80 and 6809 to 68000 as
complexity and sound and color advanced, and there were a few games
here and there with something odd like a 6502, but the rare appearance
of a T-11 really stood out for me. I never played Paperboy much, and
I haven't seen too many of the machines in the wild since I learned
they hid a T-11 inside.
-ethan