FA-PDT-11/150 on eBay

From: Megan <mbg_at_TheWorld.com>
Date: Tue Jun 3 08:48:00 2003

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

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

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

>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).

>Also, the Qbus is probably limited and can't actually
>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

>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!

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
Received on Tue Jun 03 2003 - 08:48:00 BST