From: Johnny Billquist

>On Tue, 11 Jan 2005, Stuart Brook wrote:

[...]
>> If memory serves, wasn't that an FE PDP-8 ? PDP-10s were out long befo=

>re 11s.
>
>Oh, and KLs came out long after the first PDP-11. :-)
>KL-10s normally have an 11/40 as FE. I wonder if the PDP-8 FE might have=20
>been for some other PDP-10, but then again, did any other PDP-10 have a=20
>"real" FE?


I don't think anything else had a "real" FE unless you count the 8080A inside
a KS10 (the purpose is the same -- minor I/O and to spoon feed microcode
to the main CPU since the microcode is in RAM, the KA/KI weren't microcoded
so that didn't come up with them). But PDP-8s were definitely used as I/O
processors in the earlier machines (so I guess that's *an* FE, as opposed
to *the* FE). The number 680I just popped into my head, did I make that up?
Anyway I think there was some kind of deal with a PDP-8/I acting as a bunch
of software UARTs. Also on the KLs they had PDP-11s as I/O processors
(besides just the FE 11/40), I've seen 11/34a CPU boxes with a sticker over
the "pdp-11/34a", and they had various names depending on the config (were
there ANxx and DNxx numbers for network processors, or did I imagine that?).

DECtape -- exactly, KL model A CPUs (or at least, the one at my old job)
had DECtape for the FE to boot from but that's different from honestly,
truly having DECtape that's run by the PDP-10 itself. I think DEC was
fairly adamant that DEC-20 systems couldn't have DECtape, no idea why
since of course there was no hardware reason why not (well for the KS
you'd have to ECO a TC11 to include the 2 MSBs in DMA, but there's a slot
or two free in the TC11 backplane and bit 14 of the command register is
unused so it ought to be possible to do an 18-bit mode pretty neatly).
But, DEC always liked to burn bridges to the past at regular intervals.

Other cancellation dates -- I remember hearing about the 11/70 being
canned when I was in late high school, so I'd guess 1983-1984 for that
(assuming I heard right).

John Wilson
D Bit
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