Subject: FA-PDT-11/150 on eBay

From: "Stuart Johnson" <[email-masked]>
Date: Sat May 31 18:12:11 2003

I noticed this on eBay and thought I'd post it here for those PDP-11
collectors among us:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2733136922&category=1247

The starting price ($199 US) seems high, but these are pretty hard to find.
One possibly sour note though - the seller wants a flat rate of $150 to ship
anywhere in North America.

I picked up one of these in terrific condition last December for $25. It cost
$65 to pack and ship the heavy thing, but it was worth it. I haven't seen
another PDT sell since then.

Stuart Johnson

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From: Ethan Dicks <[email-masked]>
Date: Mon Jun 2 07:57:17 2003

--- Stuart Johnson <[email-masked]> wrote:
> I noticed this on eBay...The starting price ($199 US) seems high, but
> these are pretty hard to find.

I used to have one, but I sold it about 10 years ago (for around $40,
IIRC).  I didn't think I'd ever use it (didn't know about formatting
blank 8" floppies in it, or I'd never have sold it).

> One possibly sour note though - the seller wants a flat rate of $150 to
> ship anywhere in North America.

Yow!  I can just about get a round-trip ticket to Burbank for that (not
quite, but close).

> I picked up one of these in terrific condition last December for $25. 

Nice.  Even with the shipping.

-ethan

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From: "Zane H. Healy" <[email-masked]>
Date: Mon Jun 2 07:57:19 2003

>anywhere in North America.

Interesting.  It's in identical shape to the one that I've got.  I've been wondering how much one would sell for if it was fixed up a little.  However, I think the outrageous shipping charge and unknown condition will prevent him from getting what he could for it.

			Zane

-- 
--
| Zane H. Healy                    | UNIX Systems Administrator |
| [email-masked] (primary)    | OpenVMS Enthusiast         |
|                                  | Classic Computer Collector |
+----------------------------------+----------------------------+
|     Empire of the Petal Throne and Traveller Role Playing,    |
|          PDP-10 Emulation and Zane's Computer Museum.         |
|                http://www.aracnet.com/~healyzh/               |

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From: "Jerome H. Fine" <[email-masked]>
Date: Mon Jun 2 07:57:54 2003

>"Zane H. Healy" wrote:

> Interesting.  It's in identical shape to the one that I've got.  I've been wondering how much one would sell for if it was fixed up a little.  However, I think the outrageous shipping charge and un…

Jerome Fine replies:

When Megan Gentry mentioned that the PDT-11/150
is able to do a LLF (Low Level Format) on the 8" floppy
media, I asked about the possibility of a hard disk drive.

Does the PDT-11/150 use the DX.SYS device driver
to run the RX01 floppy media?

I know there is a device driver called PD.SYS, but I am
not sure what it supports.

Also, from what I understand, the PDT-11/150 can run
RT-11, but not RT11XM, only RT11SJ and RT11FB.
And the maximum memory is probably 64 KBytes with
the IOPAGE taking either 8 KBytes (or 4 KBytes?).

Sincerely yours,

Jerome Fine
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From: Megan <[email-masked]>
Date: Mon Jun 2 07:57:58 2003

>to run the RX01 floppy media?

No, it uses PD.SYS... and the actual code which does the
hardware control is pretty much in ROM... the PD driver
calls the ROM, and the ROM knows about RT-11 queue
elements.  It returns with either success or failure.

>the IOPAGE taking either 8 KBytes (or 4 KBytes?).

The actual memory layout is 60kb with a 4kb IOpage.  It
does not have a memory management unit, so RT11SB and FB
are the only ones which run on it.

					Megan

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From: "Jerome H. Fine" <[email-masked]>
Date: Mon Jun 2 07:58:10 2003

>Megan wrote:

Jerome Fine replies:

Thank you!

That accounts for the ability to be able to do the LLF.

> are the only ones which run on it.

Is there an actual Qbus - or something else?  It certainly
sounds like a Qbus!

But without extra memory, let alone an MMU, there
also can't be a VM: either?

Also, I presume there is no possibility of a hard drive?

Also, the Qbus is probably limited and can't actually
have any additional boards?

How many DL ports are available?

Finally, my guess is that SIMH could emulate the PDT-11/150
since all that would be required is the PD.SYS device driver.
But I doubt that there is much of a reason to do so!

Sincerely yours,

Jerome Fine

---

From: Megan <[email-masked]>
Date: Tue Jun 3 16:11:24 2003

>Is there an actual Qbus - or something else?  It certainly

No, the CPU board, memory and terminal interface board are
a unit of 3 boards connected together.  The disk interface
is a separate board.

>There is no MMU, which the VM handler requires.

>Also, I presume there is no possibility of a hard drive?

I would not say no possibility, since I'm sure someone with
the skill could hack something together, even if it was to
take replace the floppy interface board with something that
looked like a floppy to the CPU, but was actually a hard
drive.

But, if you are asking about any designed-in way of expanding
with a hard drive -- no.  The PDT is a bounded system *

	(* Bounded system - a system which would be usable
	   if it could be expanded, but can't because it is
	   bounded).

>have any additional boards?

There is no bus.  The boards don't plug in anyplace, they are
simply attached back-to-back (with the exception of the floppy
interface board, which has a wire/ribbon cable (? - it has been
awhile since I opened one up) connecting it.

>How many DL ports are available?

One Console port (standard CSR/Vector), three async serial
ports (I forget which range they are -- I can check), one
printer port, and one modem port which is either sync or
async

>But I doubt that there is much of a reason to do so!

To accurately emulate it, someone would need to dump the ROM
code and use it to process the RT requests.

Another gotcha in the PDT is the slooowwwww IOpage accesses...

If you do a word access, it takes 90ms (if I remember correctly),
but a byte access takes 180ms.  Also, there is something about
read-modify-write instructions, you don't want to use lots of
them on the PDT in interrupt code... I seem to remember code
somewhere which has PDT conditionals to govern whether the
code uses MOVs or BISs, the latter being avoided on the PDT.

					Megan