The power system for the memory was the really bad thing in the KL. It was a big straight transformer. I had to replace it once, and it was heavy as hell. No switched stuff in sight for that one.

On 2023-03-26 21:15, Thomas DeBellis wrote:

Thanks, I had a look; this is 'just' for the processor complex, so I have yet to scare up the peripherals.

The first three cabinets are the processor, I/O control, memory and communications (PDP-11/40 front end) complex. These alone accountfor

21.6 kilowatts. Ouch... Of course, that's without the peripherals.

CU20B had a 3 pack RP06 PS: (boot) structure (email, staff and client storage) and other executables), an RP07 CU: structure (staff usage),

an RP06 SNARK: structure (Monitor, Exec and Galaxy sources) and a free RP06 for client disk mounts. It had a pair of TU78 (6250 BPI) tape

drives plus two more PDP-11 front ends for WAN DECnet and IBM communications.

Finally, it had a stack of RA81's for the common file system and associated CI and STAR connector. I can't remember what we kept on

those; they were not initially all that reliable (neither was the RP07), come to think of it. I'm probably forgetting something. I would say all of that shit easily doubled things, so I guess you're talking 50 kilowatts.

CompuServe came up with another power supply which I would assume was a switcher; it halved the power requirements. They offered to license it to DEC for free, but apparently DEC didn't take it because it was too late into the KL product life cycle. I heard of other sites usingit, but I think you had to have your own internal Field Service personnel. CMU did that, but I'm not sure if it was for the power supplies.

I once heard of some guy who managed to get a KA10 (just the processor complex) into his apartment. This was a building that was so old that

it didn't have separate meters for each apartment (!!). While he could only run it during the winter (with the windows wide open), he didn't get nailed for the power.

Having once inhabited in an older (WWII) Queens (LIC) apartment, I'm not sure how he would have done that without melting the wiring, so maybe this is apocryphal.

------------------------------------------------------------------------

On 3/26/23 2:19 PM, Paul Koning wrote:

Bitsavers has some stuff in the pdf/dec/pdp10/KL10 directory, including EK-PWR20-SD-001_DEC20_PowerSysDescr_Apr76.pdf <http://bitsavers.org/pdf/dec/pdp10/KL10/EK-PWR20-SD-001_DEC20_PowerSysDescr_Apr76.pdf> which describes the power supply subsystem. That mentions power requirements. Yes, 208 volt 3-phase at 60 amps per phase...

I think those are linear supplies, so they aren't as efficient as switchers.

paul

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On Mar 26, 2023, at 1:11 PM, Thomas DeBellis <tommytimesharing@gmail.com> wrote:

I got asked what the power requirements would have been for 1985 vintage KL10 based system.

Does anybody know where I would be able to find such information? I had thought it was in the site installation guide, but I haven't found an online version, yet.

About the only thing I can remember is that it was three phase power and that the power supplies were very inefficient.

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