[rescue] FA: PDP11 Qbus cards CPU and Memory

[Dave McGuire]

On March 25, Fogg, James wrote:
> Momma told me to never stick my hand into a dogfight, but here goes...
> 
> !!!DISCLAIMER!!! I am NOT a DECspert, I don't even play one on TV.

  Don't worry about it James, you're not an asshole. :-)

> This page http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?PDP-11 does make it
> sound like there was a LSI-11 model.
> 
> This page might (need character sets to see fully)
> http://openvms.compaq.co.jp/history/digital/40th/pdph.html

  In both of these cases, they're talking about processor
implementations, not systems.  The introduction of Qbus systems marked
a transition from a processor that's a "box" to a processor that'a
"board".  A PDP-11/04 processor, for example, is either a 5.25" or
10.5" rackmount chassis...what makes it a PDP-11/04 is one board, the
backplane, and the front panel (and possibly one more board depending
on the type of front panel in use) (which are also used with the
/34)...but when one spoke of a "PDP-11/04" one could either refer to
the processor box or the entire system.  With the introduction of the
Qbus systems, the processor was an "LSI-11" (of various types) and the
whole system was a "PDP-11/<whattever>".

  I believe this is reflected in terminology in these pages, albeit
somewhat loosely.

  See my mention of the PDP-11/24 in my other recent email for another
example of this.

> And these.. http://www.parse.com/~pdp8/spares.html

  This guy made the same mistake that Greg did.  Not that it's a big
deal; Greg's attitude was far worse than the specifics of his error.

> http://www.iana.org/assignments/machine-names 

  ...also in this list is "M68000", which is (as we all know) the name
of a processor, not a computer.

> And yet this listing of DEC models doesn't
> http://www.psych.usyd.edu.au/pdp-11/models.html

  Yup.

> And here's a photo of what appears to be a DEC OEM product called the LSI-11
> http://simh.trailing-edge.com/photos/lsi11.jpg

  The term LSI-11 referred to chipsets and processor boards...sometimes
an OEM-able processor "assembly" (my term, not DEC's) was called
"LSI-11", it consisted of a backplane and card cage, an LSI-11
processor, memory, and potentially some I/O depending on how it was
ordered.  This was intended to be an embeddable processor assembly,
treated as a single unit, in much the same way as one might use an
8051 or a PIC microcontroller.  We don't refer to that 8051 or PIC as
a "computer", but as a "microcontroller" or a "processor".  See what I
mean?

> If one is mostly familiar with DEC products from Internet archives, I can
> definately see why one would think there was an LSI-11 model. I found the
> research most confusing. Personally, I have never heard of one.

  Indeed, the lines are fine, but they're definitely there.  In Greg's
defense (hell, SOMEONE needs to defend that boy) I will say that this
is a fine point, and an easy mistake to make given nothing but the
resources of enthusiasts' web pages.

         -Dave

-- 
Dave McGuire                    "...it's leaving me this unpleasant,
St. Petersburg, FL                 damp feeling on my shorts..." -Sridhar