VAXen with switchmode power supplies? - DEC

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  1. VAXen with switchmode power supplies?

    Did any of the early VAX machines use a switchmode power supply?

    Or were they "traditional" power supplies?

    As far as I know, the Apple ][ from 1977 was the first microcomputer to
    use such a power supply but who used them first in "real" computers?

    IBM? DEC? DG?

    Wouldn't it have been worth it to use a switched mode power supply because
    of their higher efficiency, leading to less heat to remove from the
    machine room and smaller power bills?

    -Peter

  2. Re: VAXen with switchmode power supplies?

    In article , Peter
    \"Firefly\" Lund wrote:

    > Did any of the early VAX machines use a switchmode power supply?
    >
    > Or were they "traditional" power supplies?
    >
    > As far as I know, the Apple ][ from 1977 was the first microcomputer to
    > use such a power supply but who used them first in "real" computers?
    >
    > IBM? DEC? DG?
    >
    > Wouldn't it have been worth it to use a switched mode power supply because
    > of their higher efficiency, leading to less heat to remove from the
    > machine room and smaller power bills?
    >
    > -Peter

    PDP8 F or was it M? had a switched mode power supply. That would have
    been about 1973 I saw the first of them. You could tell it by the
    whistle it made. It varied on load.

    --
    To de-mung my e-mail address:- fsnospam$elliott$$
    PGP Fingerprint: 1A96 3CF7 637F 896B C810 E199 7E5C A9E4 8E59 E248

  3. Re: VAXen with switchmode power supplies?

    On Fri, 1 Sep 2006, Elliott Roper wrote:

    > PDP8 F or was it M? had a switched mode power supply. That would have
    > been about 1973 I saw the first of them. You could tell it by the
    > whistle it made. It varied on load.


    Nice

    Was it good? Too big anyway? Broke too easily? Hard to repair?

    -Peter

  4. Re: VAXen with switchmode power supplies?

    In article , Peter
    \"Firefly\" Lund wrote:

    > On Fri, 1 Sep 2006, Elliott Roper wrote:
    >
    > > PDP8 F or was it M? had a switched mode power supply. That would have
    > > been about 1973 I saw the first of them. You could tell it by the
    > > whistle it made. It varied on load.

    >
    > Nice
    >
    > Was it good? Too big anyway? Broke too easily? Hard to repair?


    PDP8 e f and m were built like brick ****houses. They never broke.

    --
    To de-mung my e-mail address:- fsnospam$elliott$$
    PGP Fingerprint: 1A96 3CF7 637F 896B C810 E199 7E5C A9E4 8E59 E248

  5. Re: VAXen with switchmode power supplies?

    Peter "Firefly" Lund wrote:
    > Did any of the early VAX machines use a switchmode power supply?
    >
    > Or were they "traditional" power supplies?
    >
    > As far as I know, the Apple ][ from 1977 was the first microcomputer to
    > use such a power supply but who used them first in "real" computers?
    >
    > IBM? DEC? DG?
    >
    > Wouldn't it have been worth it to use a switched mode power supply
    > because of their higher efficiency, leading to less heat to remove from
    > the machine room and smaller power bills?
    >

    Singer System-10 had a switcher on its 5V rail. This wasn't off-line:
    everything came through a huge iron transformer, then was regulated at
    LT. The other rails (less load) used linear regulators.

  6. Re: VAXen with switchmode power supplies?

    On Fri, 1 Sep 2006, Elliott Roper wrote:

    > PDP8 F or was it M? had a switched mode power supply. That would have
    > been about 1973 I saw the first of them. You could tell it by the
    > whistle it made. It varied on load.


    http://www.pdp8.net/pdp8em/h724.shtml

    "The PDP-8/E computer used the h724 linear power supply. This machine was
    the last that used a linear power supply. The later 8/M and 8/F machines
    used the h740 switching power supply. "

    Turns out both were right

    http://www.faqs.org/faqs/dec-faq/pdp...section-9.html

    "What is a PDP-8/F?

    Date of introduction: 1972.
    Date of withdrawal: 1978.

    Technology: an OMNIBUS machine, as with the PDP-8/E. First use
    of a switching power supply in the PDP-8 family.
    "

    "The original PDP-8/F box had a defective power
    supply, but a revised (slightly larger) box corrected this
    problem."


    It looks like the VAX 11/750 (1981) also had a (partially) switched-mode
    power supply:

    http://vt100.net/manx/details/1,2242

    (it takes a bit of reading into the PDF to get the block diagrams and the
    talk about the 20 kHz pulses.)

    So, my next question is: does anybody have any idea of the efficiency of
    those power supplies?

    -Peter

  7. Re: VAXen with switchmode power supplies?

    Peter "Firefly" Lund wrote:
    > Did any of the early VAX machines use a switchmode power supply?
    >
    > Or were they "traditional" power supplies?
    >
    > As far as I know, the Apple ][ from 1977 was the first microcomputer
    > to use such a power supply but who used them first in "real" computers?
    >
    > IBM? DEC? DG?
    >
    > Wouldn't it have been worth it to use a switched mode power supply
    > because of their higher efficiency, leading to less heat to remove
    > from the machine room and smaller power bills?
    >
    > -Peter

    IBM went through all sorts of power supply systems in their mainframes
    (I've pulled apart many of them).

    Not sure when it was made, but the IBM 370/115 that I began working with
    in 1979 had switchers. About 8 of them, a little larger than a car
    battery. They were modular units in plastic enclosures that could be
    easily disconnected and replaced.
    I still have most of them in my shed! The 5 volt unit is rated at 85 amps.

    The later 4341 machines reverted back to linear supplies.

    3031's had a weird type of switching rectifier system. A motor/generator
    set converted mains to some lower 3-phase voltage at 400Hz, which was
    then distributed to local (very heavy) regulator units that used six big
    SCR's and a very large filtering inductor.

    I suppose each manufacturing division had their own favorite power
    supply topology.

    Rob Storey

  8. Re: VAXen with switchmode power supplies?

    Rob writes:
    > 3031's had a weird type of switching rectifier system. A
    > motor/generator set converted mains to some lower 3-phase voltage at
    > 400Hz, which was then distributed to local (very heavy) regulator
    > units that used six big SCR's and a very large filtering inductor.



    the 3031 were just a repackaged pair of 370/158 engines. the 158 had
    microengine with programming that did both 370 instruction set
    emulation and also the integrated i/o channels. for the 303x line
    (3031, 3032, and 3033), they took a 158 engine with ONLY the
    programming for the integrated channels and packaged it as the
    "channel director" (i.e. independent engine providing channel function
    for all processors in the 303x line.

    so a 3031 was repackaged 158 with a pair of 158 engines ... one
    dedicated to 370 operation and one dedicated for channel operation.

    a 3032 was a 370/168-3 repackaged to use channel director

    a 3033 started out being 168 wiring diragram mapped to newer hardware
    technology (and using channel directors).

    a two-way 3031 smp multiprocessor would have a pair of 158 engines
    doing 370 instruction set and a second set of 158 engines dedicated as
    channel director (for total of four 158 engines).

    a picture of 3033 mentioning motor generator
    http://www.grouchyoldcripple.com/archives/001620.html

  9. Re: VAXen with switchmode power supplies?

    On Fri, 15 Sep 2006, Rob wrote:

    > I still have most of them in my shed! The 5 volt unit is rated at 85 amps.


    Ouch!

    > The later 4341 machines reverted back to linear supplies.


    Huh? How come?

    > 3031's had a weird type of switching rectifier system. A motor/generator set
    > converted mains to some lower 3-phase voltage at 400Hz, which was then
    > distributed to local (very heavy) regulator units that used six big SCR's and
    > a very large filtering inductor.


    For other people who didn't know about SCRs:

    http://en.wikipedia.org/wiki/Silicon...lled_rectifier

    -Peter

  10. Re: VAXen with switchmode power supplies?


    Peter "Firefly" Lund wrote:


    > As far as I know, the Apple ][ from 1977 was the first microcomputer to
    > use such a power supply but who used them first in "real" computers?


    The CDC 160A, circa 1961 had a switching power supply. The slow
    transistors of the day meant it had to switch at about 700 Hz, but it
    was a switching PS. You could hear it whine. It was mounted in the
    right desk drawer.

    The shoebox sized MicroVax line of course had a SMPS. A very HEAVY and
    DENSE SMPS.


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