KL10-A/KL10-B differences

Eric Smith spacewar at gmail.com
Tue Jul 9 18:31:15 CDT 2019

On Tue, Jul 9, 2019 at 4:44 PM Noel Chiappa via cctalk <
cctalk at classiccmp.org> wrote:

> Could an -A be upgraded to a -B by swapping the I/O backplane?

Electrically, yes, but physically it might not be easy. The portions of the
chassis that support the backplanes are different, and the power supplies
aren't there.

When I refer to "I/O backplane", technically that's four separate
backplanes. There's one DIA20/DMA20 backplane (not present in all models),
one DTE20 backplane, and two separate backplanes that are combined for the
RH20s (if present), one backplane for the A through D positions (upper 2/3
of each module slot), and one for E and F.

The KL10-A (DECsystem-1080) does not have the RH20 backplanes, and has a
variant of the DTE20 backplane that only supports a single DTE20. The
KL10-A I/O cabinet has only 7 DC power supplies and associated cabling, vs
13 for the KL10-B, because it only has to power one DTE20 rather than four
DTE20s and eight RH20s. Because of that, the KL10-A has only two H742 power
supply frame/front-end assemblies rather than three.

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

Essentially andom, as far as I know. KL10-PB through KL10-PD are assigned
to some kind of subassemblies, but are not the same kind of assembly as the
-PA and -PV. Probably a lot of -Px were assigned before they got to needing
one that became -PV.

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'm not entirely sure, so I easily could have been mistaken. I know -PV to
-PW just needs some wraps. -PA to -PV may have required more significant
backplane changes. Definitely they have different part numbers for the -PA
and -PV backplane assemblies.

I've also got some open questions on the later things like the KL10-R,

AFAIK, -R is functionally and electrically equivalent to -E, but with
physical changes needed for FCC compliance.

> -PW,
> and MCA25,

The MCA25 is the upgrade from -PV to -PW. It's preinstalled on the 1095 and

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