HP stuff (was HP's not cool)

From: Jay West <west_at_tseinc.com>
Date: Mon Nov 22 21:25:30 1999

Eric wrote...
> You certainly didn't have to remove memory cards from a PDP-8 to add I/O
> cards. Or, for that matter, from the PDP-4, PDP-5, PDP-7, and PDP-9,
> I also claim to be the intellectual forebears of the HP 21xx. Where on
> did you get that idea?

Yes, you do have to remove memory cards from a PDP-8 to add I/O cards, *IF*
your backplane is full. So in many architectures there was always a decision
to be made about having too many io cards for the memory amount you wanted
or vice versa. Of course, with the -8 you can always add another internal
backplane, but that's hardly an elegant solution.

> In terms of the instruction-set architecture, it clearly was derived
> from the DEC 18-bit and 12-bit architectures.

I know both instruction sets well (albeit HP's much better). I don't find
the 21MX instructions to be any more or less like the -8 than most any other
machine out there. I suspect that the 21MX set is similar not because of
the -8 being a "forefather", but because most instruction sets have a large
number of similarities on any set of machines (except Pick virtual
assembler, that is truely a unique animal). I just can't agree that the 21MX
instruction set was derived from the 12 bit DEC stuff. There's nothing
unique about the DEC set that is in the HP set.

> the 21xx instruction set architecture any less of a decendent of the DEC
> machines. And it's not surprising, since HP used a lot of PDP-8s before
> they decided to get into the computer business themselves.

Ok, I have to challenge you here. Other than basic instruction set
similarity, do you have any historical evidence that the 21xx instruction
set was derived from the DEC machines? I'd love to hear it....I'm always
willing to change my position in the face of facts. But just based on
instruction set similarities? Hum....

> As is usual around here, (e.g., the flame war over the word "obsolete"),
> people seem to associate way to much emotional baggage with simple terms
> and phrases.

Ok, so I'm touchy about my treasured HP's <grin>. But only because it seemed
you said they were directly derived from 12 bit decs, and I have not now or
ever seen any evidence of that. I really didn't intend to start a HP vs. DEC
war. I think they're both great machines. But don't say my machine is only
great because yours is! :)

Jay West
Received on Mon Nov 22 1999 - 21:25:30 GMT

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