Portable PDP-11 (was Re: Does anyone use RT-11?)

[Allison]

>
>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 13:55:56 -0500
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On 9/10/07, Allison <ajp166 at bellatlantic.net> wrote:
>> >   "Ethan Dicks" <ethan.dicks at gmail.com wrote:
>> >
>> >On 9/9/07, Allison <ajp166 at bellatlantic.net> wrote:
>> >> 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...
>>
>> I have a lot on paper plus the ever important T-11 manual.
>
>Very handy.

Required! ;)


>>  However
>> it has stopped at that phase mostly due to other projects having
>> my interest.
>
>Fair enough.  I think most of us have a variety of projects cluttering
>our foreground task.
>
>> ... only 8KW ram, 8KW Eprom and a DLART for serial IO.
>
>Certainly minimal, though today, 28KW of RAM isn't a stretch.

At the time I was just hacking and wanted to use the smaller parts I had
for simplicity reasons.

>> 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.
>
>Understandable.
>
>> >As for storage, obviously some flavor of FLASH is great for most
>> >things...
>>
>> None of the above for cost or availability reasons.  I'd opt for IDE
>> using one of the many 40-500mb drives I have.
>
>That's certainly a larger device than I'd envisioned (my initial idea
>was a "pod" the size of a modem or smaller, with an external
>display/keyboard/host port).
>
>> >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...
>>
>> I planned on text.  However it's possible to get LCDs used for laptops
>> but the logic to drive them is non trivial.
>
>Yes.  I have a 640x400 laptop display, with specs, that ran me about
>$10 a few years back.  If I ever decide to learn VHDL, I might try to
>interface it to my IOB6120, but, yes, it takes a bit of work to talk
>to those.

I ahve three of them, monchrome.  They are easy enough to drive but the 
little "gotchas" are nasty.  First one is the display is really two 
640x240 segments running in parallel top and bottom so there are two
"video" data paths running concurrently unlike a CRT.  If your doing 
bit mapped (1BPP) that's some 40k of total memory to address, oh and 
that has to really two memories or a funny dual output scheme to feed
the display.  Doing character only simplifies it some if you don't 
mind doing some logic twice (font, bit shifter, memory).

>> >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...
>>
>> 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.
>
>Interesting.  I suppose it couldn't be _too_ complicated, then, since
>it one like it does fit on a few square inches of  11/34 CPU board.

Basic circuit is the same.

>I even happen to have a small pad of 74189s.

Same here.

>
>> 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.
>
>Hmm... from what I've seen of CUBIX, it sounds feasible for a PDP-11
>host, and it certainly gets around the issue of what OS to distribute,
>but I would think that porting CUBIX could be an entirely independent
>project (focusing on whatever display and mass-storage interfaces are
>available).

The OS can be logically seperated from the mass storage and addressed
as a series of logical blocks so that going to floppy, IDE or whatever 
is easy as most do (or can do) 512byte sectors as a consistant thing.
That divorces the CHS/LBA thing from the os.

> > >So, Allison, does any of this sound like what you had in mind... ?
>>
>> 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.
>
>I hadn't specifically been requiring a laptop shape, more of a tiny
>luggable - on the order of one of the modern Tektronix LCD-screen
>digital scopes.

totable. ;)

>> 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.
>
>OK.  I'm not sure I get the "VK170" reference.  Is that some sort of
>DEC or 3rd party embedded product?

VK170 was a DEC Qbus/Ubus card that did RS232/423 IO and had outputs for 
RS170 video or Video/Hsync/Vsync and took a parallel keyboard to serial
(used LK02 or similar).  The bus edge connector was power only so it 
could even be externally mounted as a minimal VT52 (80x25). It's in 
the Microcomputer handbooks.

>Thanks for sharing your design ideas.

They aren't patented. ;)


Allison