Jerome H. Fine jhfinedp3k at compsys.to
Fri Jun 3 21:59:13 CDT 2016

 >Henk Gooijen wrote:

> -----Oorspronkelijk bericht----- From: jwsmobile Sent: Friday, June 
> 03, 2016 7:51 PM To: General Discussion: On-Topic and Off-Topic Posts 
> Subject: Re: PDP-11/94-E
> On 6/3/2016 9:11 AM, Jerome H. Fine wrote:
>> >Rod Smallwood wrote:
>>> >On 03/06/2016 16:43, Jerome H. Fine wrote:
> <snip>
>>> Hi its a KDJ11-B all memory on CPU board
>>> Rod
>> I am very confused.  Is your mention of memory on the CPU board
>> for the PDP-11/83 or the PDP-11/93?  I thought that the PDP-11/83
>> never had memory on the CPU board (assuming that the cache is not
>> regarded as memory).
>> This aspect of the thread is probably no longer relevant, I just wanted
>> to note that PMI memory can be used with what most individuals would
>> consider to be a PDP-11/73 (naturally a quad) board and the PMI
>> aspect of the memory will be activated when the PMI memory is
>> installed ABOVE the CPU board.
>> Also when PMI memory is installed BELOW the backplane, it is then
>> used as normal Qbus memory in a Qbus system.  I can't see anyone
>> doing that, but it is allowed.
>> Jerome Fine
> I suspect it is using this board.
> http://www.ebay.com/itm/161791207076
> I am guessing the 1.5mb isn't cache, but is system memory on this board.
> There is also the KDJ11-BF which has no memory on board.  M8190-AE.
> thanks
> Jim
> ----
> Nope, the M7554 is the PDP-11/53 CPU.
> The 11/83 had its memory on the bus (either left or right of the module).
> The 11/94 did NOT have memory on the bus, because *all* memory is
> on the CPU module itself. Note that there are two versions of the 11/94.
> One with 2 MB RAM and one with 4 MB RAM (all that can be addressed!).
> The 2 MB version and the 4 MB version are identical, just half the RAM 
> chip
> population is not placed. However, all through-hole pins are soldered so
> the upgrade from 2  MB to 4 MB would be a real PITA, *if* you'd try it 
> at all!
> - Henk

Thank you for the clarification.  I knew that the PDP-11/53 held on board
memory, but I just could not remember that the last two digits were "53".

One other minor clarification that probably most remember, but maybe a few
individuals don't.  The CPU boards for both the PDP-11/83 and the PDP-11/93
are almost always used in Qbus only systems.  In very rare situations, a 
may also be present to support using the system with Unibus hardware, 
but that
situation would be unusual.

The PDP-11/84 and PDP-11/94 use the identical CPU boards, but are
configured to include a Qnivertor (as Rod Smallwood mentions in another
post) and would rarely include any Qbus boards.  In addition, for the
PDP-11/84, the PMI memory is different from the memory used in the
PDP-11/83 and there are probably no free Qbus slots for any additional
Qbus boards.  For the PDP-11/94, there seems to be a couple of free slots
still available, but since they are not normal Qbus slots (they are 
designed for the PMI memory used in the PDP-11/84 after all), standard
Qbus boards may not work correctly.

I just wanted to mention those aspects for PDP-11/83, PDP-11/93,
PDP-11/84 and PDP-11/94 users.

Please mention if I have made any mistakes in my description.

Jerome Fine

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