10 Sep
2007
10 Sep
'07
11:18 a.m.
Subject: Portable PDP-11 (was Re: Does anyone use RT-11?)
From: "Ethan Dicks" <ethan.dicks at gmail.com>
Date: Mon, 10 Sep 2007 11:54:54 -0500
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
On 9/9/07, Allison <ajp166 at bellatlantic.net> wrote:
I have a lot on paper plus the ever important T-11 manual. However
it has stopped at that phase mostly due to other projects having
my interest. I did some prototyping a few years back with the T11
to see in in action without a lot of DEC hardware around it. I
have that but it was never meant to grow and is only 8KW ram, 8KW
Eprom and a DLART for serial IO. Since then I've been doing 8085,
Z80, Z280, 6809 and 1802 stuff when not building HF and VHF tranceivers.
One day I plan to get a T11 up and running wtih
RT but with non-DEC
drivers for terminal and storage as a small toteable -11.
I'd like to hear more about this, either on-list, if you feel your
ideas are fleshed out enough to share widely, or off-list, if you are
not as far along with the creative process. Ever since I had a PDT-11 (and let it go to another
collector, sadly
for me), I've wanted a portable PDP-11. It might or might not be easy
(read inexpensive ;-) to implement an 80x24 LCD, some form of 40x25
isn't expensive at all since it only takes a 320x200 mono LCD panel.
Of course, one could just have serial out from the basic PDP-11
design, then worry about a portable display as a secondary project.
The display is really the harder part at least for portability and power
consumption. However for this one I was considering packaging along
the lines of the Kaypro totables and wall power. Part of this recognizes
the T-11 uses a fair amount of power (Z80 NMOS is similar) and most of
the parts around it will not be CMOS so battery operation is not easily
accomplished.
As for storage, obviously some flavor of FLASH is great
for most
things. CF is easy to interface to, and CF cards 1GB and smaller are
quite inexpensive. MMC/SD are also inexpensive and even easier to
interface to, with a bit more work on the driver side to man the SPI
interface.
None of the above for cost or availability reasons. I'd opt for IDE
using one of the many 40-500mb drives I have.
While textual LCDs are cheaper and easier to interface
to, the largest
one I've seen is 4x40. A graphical LCD panel with a SED1335 or t6963
of a size of 640x200 would be perfect for 80x25, and, since the common
graphical LCD controllers are well documented, not difficult to talk
to. One could either attach the graphical display right to the T-11
bus as a peripheral and do all the work in PDP-11 software, or hang a
microcontroller off of the T-11 via serial, and write some
microcontroller firmware to turn the LCD into an ANSI terminal.
I planned on text. However it's possible to get LCDs used for laptops
but the logic to drive them is non trivial.
Back to the T-11, though, if I recall its capabilities
correctly, it
doesn't have an MMU, and it would be difficult, if not impractical, to
design an external one that resembles, say, the MMU on an 11/23... so
that means RT-11SJ monitor only, correct? (or would FB be possible?)
There's lots of software out there that runs in 56K or less, so I
don't see that as a fatal flaw.
Correct on the OS and software. However the MMU is very buildable
and not near as hardware intensive as would seem. For an example
look at the T-11 interface in the VT240. It takes a few 16x4
bipolar rams and some loose logic to implement the paging (2 74189,
3 74ls257 and a bit of TTL glue) to make a a compatable (mostly) mapper.
One of the things I've given consideration to in recent years is a nonDEC
and non *nix OS such as CUBIX as that would translate reasonably from
6908 to PDP-11. This arises from the fact that RT-11 has a very
primitive filesystem compared to CP/M and an OS that is not encumbered
would be easier to work with.
So, Allison, does any of this sound like what you had
in mind, or am I
going off in an entirely different direction?
You envision what sould like a Laptop. I can't easily fabricate that
but a toteable like Kaypro, Osborne and a few others is very doable.
The basic machine description is a 128kW using 32kx8 static parts (8pcs),
Boot roms/ODT, MMU, two serial, parallel (PC conpatable for printer)
and IDE disk. Things like OS in Eprom have surfaced to my idea pool
to consider especially if it were not RT11 (CUBIX influence). Terminal
logic would be VK170 (base VT52 on a dual size card) and a monitor in
the 7-9" size.
Right now it's a static project from the build it perspective but
as new ideas surface and other projects supply different expereinces
it morphs some. What I'd have built say 6 years ago and noew would
be very different. It will eventually get attention as I have parts
stored away for it.
Allison
-ethan