Portable PDP-11 (was Re: Does anyone use RT-11?) - test-drb@ccmp.vtda.org

10 Sep 2007

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Subject: Re: Portable PDP-11 (was Re: Does anyone use RT-11?)
   From: "Ethan Dicks" <ethan.dicks at gmail.com>
   Date: Mon, 10 Sep 2007 12:43:52 -0500
     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>

On 9/10/07, e.stiebler <emu at e-bbes.com> wrote:
  Ethan Dicks wrote:
  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. 
 Why not just use the J-11, and have it all ? 
I would think that for one thing, T-11 chips are much easier to find
than J-11 chips - DEC used the T-11 in a variety of peripheral cards
and terminals, and such.  I personally probably have half-a-dozen T-11
chips, and two J-11 chips (one Pro380 and one KDJ11 board). 
T-11 is designed along the lines of 8085 or Z280 and far easier to 
interface than J-11.  That and I have a handful of T-11s out of 
defunct RQDX1s and VT240s. If all else the T11 is 40pin DIP and 
far easier to remove and socket for wire wrap than the huge J-11.

T-11s appeared as loose parts, RQDXn controller, VT240/241, HSC50
KXT-11 and KXT-21 to name a few.  For raw volume it outnumbers the J11.
Doesn't hurt that all software design work can be done on any PDP11
but does not rely on features not available on most all -11s.

...

If course, if a project were to erupt that was some form of portable
J-11 design w/1MB or more of SRAM and some local mass storage, I would
certainly strongly consider building one, even if I had to borrow a
J-11 chip from one of my two sources.
-ethan 
J11 and 1MB of sram is not battery friendly unless one is willing to 
invest in a lot of 74HCxx parts and a big battery. 

Allison