PDP-11/23 PLUS commercial instruction set (CIS)

From: wanderer <quapla_at_xs4all.nl>
Date: Sat Aug 4 12:40:53 2001

Hello Jerome,

There are indeed 5 sockets on an 11/23+, but an 11/24 card has 7
sockets. On the card I have, socket 1 & 2 are the basic set of microms,
the third is then the FP and the CIS microm is placed in one end of
socket 4 and the other in socket 5. Since this leaves 2 more sockets
empty, it would indeed suggest that there are/could be other options
to be added.
Judging the wiring on the board, it suggests that the position is
not relevant, except the MMU & Data and Control.

Regards,

Ed

Jerome Fine wrote:
>
> >Pete Turnbull wrote:
>
> > On Aug 3, 21:56, wanderer wrote:
> > > I have an 11/24 board here with a twice the size of the regular cpu
> > > chips mounted in socket 4 & 5. Socket 3 is empty, while the standard
> > > setup contains 3 chips in socket 1,2 & 3. Would this be the CIS chip?
> > Yes, it is. It's six control chips mounted in one "double-width" 40-pin
> > package. Socket 1 is the MMU, 2 is the Data and Control package of the
> > CPU, 3 is the Floating Point. The CIS can go in 4+5 or 5+6, and 7 (or
> > anything unused by CIS) is "spare". I don't know if there was ever any
> > other "microms" for an 11/23 or 11/24. Anyone seen any?
>
> Jerome Fine replies:
>
> I have never heard of any other "microms" for the 11/23 or the 11/24, but
> that does not mean that there are none. However, none of the manuals I
> have on the 11/23 dual (M8186) or the 11/23 quad (M8189) modules
> have ever mentioned any. So I would say it is doubtful. If there are any,
> I suspect they would be a private development and that seems even more
> doubtful considering the expense.
>
> On one point I am requesting some clarification. I have in my hands both
> an M8186 and an M8189. There are five pair of sockets for five microms.
> Right now, the CPU, MMU and FP microms are present. In the past, I have
> found that the order does not seem to be important, but I have not run an
> 11/23 (either one) lately and can't remember for sure. In any case, that
> leaves just two empty pair of sockets (20 pins each) which I presume
> would be filled by ONE CIS microm which is double width and would use
> one side of pair number 4 and the opposite side of pair number 5. Is
> this interpretation correct? I did not quite understand what you stated
> above since 5+6 does not seem to exist on either 11/23.
>
> I guess that if either the MMU or the FP were not present, the CIS microm
> could be moved down, but I presume that when inserting the CIS microm,
> the port side should always go into a port set and the starboard side should
> always go into a starboard set, just as with the CPU, MMU and FP microms.
>
> Based on the geometry, it seems impossible to insert a rom into the wrong
> pair because the spacing makes that impossible although it is obviously
> possible to reverse the direction of the rom and put it in backwards.
>
> Of course, this all assumes that a CIS microm is available!
>
> I have heard that the 11/44 has CIS and that the block move instruction
> is often used instead of a loop.
>
> Sincerely yours,
>
> Jerome Fine

-- 
The Wanderer                      | Politici zijn gore oplichters.
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Received on Sat Aug 04 2001 - 12:40:53 BST

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