KL10-A/KL10-B differences

Noel Chiappa jnc at mercury.lcs.mit.edu
Tue Jul 9 17:43:51 CDT 2019

    > Erom: Eric Smith

Hey, thanks for taking the time to provide all those details.

As you no doubt saw, our emails crossed; I had managed to work out my own
what the difference was. I'd been looking at this page:


and saw the two backplanes, and assumed one was the EBox, and one the
MBox - wrong! But eventually I got it straight...

One some other points you covered:

    > The 1080 was intended to replace a KA10 or KI10 ... It only needed a
    > single DTE20 for the internal console PDP-11, and it didn't need an
    > RH20 because the disk would be attached via an RH10

Got it; makes sense.

Could an -A be upgraded to a -B by swapping the I/O backplane? (Yes, the
wiring to the I/O connectors would have to be changed too, and that might have
been too difficult.) But could the APR handle it (perhaps with one or more
board changes)?

    > The -PA and -PV designations .. are for the "arithmetic processor"
    > (APR), which is the main CPU portion of the KL10.

Useful terminology to know. Do you happen to know what 'PV' stands for -
or is it just a random letter code?

    >> my new theory is that it's the MBox ... that is the
    >> difference between the KL10-A and the KL10-B.

    > It's not just the MBOX; there are significant EBOX differences as
    > well. Various modules from the entire CPU are different, and the
    > backplane wiring is slightly different. It was possible to upgrade a
    > -PA to -PV by swapping modules and adding some wraps to the
    > backplane

Do note I said "KL10-A and the KL10-B", not 'Model A and Model B'... I
assume the APR's in the -A and -B were identical, it was just the I/O
backplane, etc which were different.

On the -PA to -PV upgrade, could the backplane really be done with some
wraps? I ask because I saw in one manual, talking about a KL10-C to -PV
upgrade, it calls for a backplane swap-out.

I've also got some open questions on the later things like the KL10-R, -PW,
and MCA25, which are not covered well in the documentation avilable in
bitsavers; do you know about the later variations?


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