PDP-11/20 vd one that just says pdp 11 what are the date differences?? OEM?

Noel Chiappa jnc at mercury.lcs.mit.edu
Mon Feb 22 06:59:55 CST 2016

    > From: Bill Degnan

    > I have an original 1969 PDP 11 brochure. In it there are two PDP 11
    > model configurations to choose from; the 10 and the 20. For me at least
    > this throws into question the whole "... the 10 first came out with the
    > 5 in 1972..." story everyone repeats over and over

This is a known 'artifact' in PDP-11 history. DEC originally used the /10
designation for a cost-reduced 11/20. They never produced any, AFAIK - I'm
pretty sure (without checking) that machine was re-labelled the /15, and those
_do_ exist (I used one BITD).

According to DEC documentation, the /15 has a KC11 processor, not the KA11 of
the /20 (although I've never been able to find out much about the KC11 - I
suspect it was a slightly modified KA11); the main functional difference
listed is that it only supports one level of interrupt, not four; power-fail
re-start is also optional, not standard.

I have this bit set that both the /15 and /20 could be had with the 'simple'
front console, that that wasn't the differentiator between them.

The later /5-/10 pairing does indeed exist - I have one of each. They are
absolutely identical except for the printing on the faceplate.


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