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Re: [midatlanticretro] IBM PC Collectors and collections

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  • Jim Scheef
    Chris, I suspect you re referring to IBM s anti-overclocking moves: Early IBM AT s ran at 6MHz on chips rated at 8Mhz. This was done purely because of IBM s
    Message 1 of 4 , Aug 3 7:43 AM
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      Chris,

      I suspect you're referring to IBM's anti-overclocking moves: Early IBM AT's
      ran at 6MHz on chips rated at 8Mhz. This was done purely because of IBM's
      conservative design philosophy. The first AT clones ran at 8MHz and were
      faster. Duh! So IBM released the AT Model 339 running at 8MHz (I had one at
      work for several years) and the clones quickly moved to 10, 12, and 16MHz.
      And so overclocking became an industry. Naturally IBM thought this was
      ~*BAD*~ and took steps in the BIOS to prevent overclocking. I do not know if
      they actually had a warning label, but a machine with such a label might be
      "more collectible".

      Early IBM monitors (and all?? computer monitors of those years) were single
      frequency. The MDA (monochrome) adapter had a higher vertical sync frequency
      than the CGA adapter so monitor damage was probably quite possible.

      The NEC Multisync was (I believe) the first multi-frequency monitor. It
      predated the VGA standard but accepted both digital (MDA, CGA, EGA) and
      analog (VGA) inputs. This would qualify as 'vintage' in my book.
      Unfortunately my NEC Multisync finally gave up a few years ago after decades
      of use on EGA and then VGA graphics. (Returning to my original digression...)
      It is still possible to fry a monitor by feeding it the wrong frequencies.
      While today's monitors are much more tolerant, today's graphics cards can do
      things undreamed of a few years ago, so caution is always warranted when
      connecting a monitor to a computer for the first time. They don't call it
      "Safe Mode" for nothin'.

      Jim


      --- Chris M <chrism3667@...> wrote:

      > early on I would say most uP's have bugs. It took
      > Motorola some time to get the 68000 correct. As to the
      > power supplies, some of the AT's had issues, can't
      > remember what, but they had warnings posted on them
      > saying this or that would happen if this or that
      > was/wasn't done. Vague I know. And it's also my
      > understanding that the original IBM mono monitors
      > would explode if they were plugged into a CGA card.
      > I'm not willing to try this though.
      > I think I may have reached my qouta for the week.
      > Evan seems to have a problem with my posts. I'll have
      > to investigate the matter further to see if the
      > problem is reconcilable.
      >
      > --- wpileggi <wpileggi@...> wrote:
      >
      > > Regarding the IBM PC, it was manufactured over a 6
      > > year span. There
      > > were quite a few changes during the production run.
      > > Hence, there are a
      > > LOT of them floating about, mostly worth nil,
      > > especially "B" models. I
      > > had examples of all of them. The first general
      > > production run had 16Kb
      > > (RAM) motherboards; the power supply and rear panels
      > > were painted
      > > black; and the 8080 CPU had a bug (shades of the
      > > much later Pentium).
      > > THOSE are the coolest and actually valuable PC's.
      > > The rest?....
      > >
      > > An interesting aside: a fellow I know who worked for
      > > IBM in Australia
      > > says the power supplies were always blowing
      > > up....the early ones
      > > didn't get the power supply quite right. Bill/KA3AIS
      > >
      > >
      > >
      >
      >
      >
      >
      > ____________________________________________________
      > Start your day with Yahoo! - make it your home page
      > http://www.yahoo.com/r/hs
      >
      >
    • Chris M
      My first (compatible) PC was an ITT Xtra XP. I don t think it would run Longhorn though. Nor Shorthorn. It had a 6mhz crystal (12 mhz I think actually). I went
      Message 2 of 4 , Aug 4 12:51 AM
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        My first (compatible) PC was an ITT Xtra XP. I don't
        think it would run Longhorn though. Nor Shorthorn. It
        had a 6mhz crystal (12 mhz I think actually). I went
        out and bought a 16, or possibly swapped it out of my
        Tandy 2000, which ran at 8mhz, and plugged it in. The
        speed differential was noticeable, not blinding
        though.
        Come to think of it the original PC divided the
        crystal frequency by 3, so I don't know what
        frequencies were required for a '286. Therefore ignore
        all the above.
        I think the IBM monitor would explode if you plugged
        it into a CGA card. This is what I've heard. Good ol'
        Big Blue. Again, don't try it at home (or work).
        The NEC created the Multisync. I found one at TCF for
        3 bucks :). Not for sale...sorry. My first one, a
        Multisync II, I still have, and it probably has about
        200 hours on the tube. It's flakey though. When I get
        a chance, I got to crack it open and have a looksee.

        --- Jim Scheef <jscheef@...> wrote:

        > Chris,
        >
        > I suspect you're referring to IBM's
        > anti-overclocking moves: Early IBM AT's
        > ran at 6MHz on chips rated at 8Mhz. This was done
        > purely because of IBM's
        > conservative design philosophy. The first AT clones
        > ran at 8MHz and were
        > faster. Duh! So IBM released the AT Model 339
        > running at 8MHz (I had one at
        > work for several years) and the clones quickly moved
        > to 10, 12, and 16MHz.
        > And so overclocking became an industry. Naturally
        > IBM thought this was
        > ~*BAD*~ and took steps in the BIOS to prevent
        > overclocking. I do not know if
        > they actually had a warning label, but a machine
        > with such a label might be
        > "more collectible".
        >
        > Early IBM monitors (and all?? computer monitors of
        > those years) were single
        > frequency. The MDA (monochrome) adapter had a higher
        > vertical sync frequency
        > than the CGA adapter so monitor damage was probably
        > quite possible.
        >
        > The NEC Multisync was (I believe) the first
        > multi-frequency monitor. It
        > predated the VGA standard but accepted both digital
        > (MDA, CGA, EGA) and
        > analog (VGA) inputs. This would qualify as 'vintage'
        > in my book.
        > Unfortunately my NEC Multisync finally gave up a few
        > years ago after decades
        > of use on EGA and then VGA graphics. (Returning to
        > my original digression...)
        > It is still possible to fry a monitor by feeding it
        > the wrong frequencies.
        > While today's monitors are much more tolerant,
        > today's graphics cards can do
        > things undreamed of a few years ago, so caution is
        > always warranted when
        > connecting a monitor to a computer for the first
        > time. They don't call it
        > "Safe Mode" for nothin'.
        >
        > Jim
        >
        >
        > --- Chris M <chrism3667@...> wrote:
        >
        > > early on I would say most uP's have bugs. It took
        > > Motorola some time to get the 68000 correct. As to
        > the
        > > power supplies, some of the AT's had issues, can't
        > > remember what, but they had warnings posted on
        > them
        > > saying this or that would happen if this or that
        > > was/wasn't done. Vague I know. And it's also my
        > > understanding that the original IBM mono monitors
        > > would explode if they were plugged into a CGA
        > card.
        > > I'm not willing to try this though.
        > > I think I may have reached my qouta for the week.
        > > Evan seems to have a problem with my posts. I'll
        > have
        > > to investigate the matter further to see if the
        > > problem is reconcilable.
        > >
        > > --- wpileggi <wpileggi@...> wrote:
        > >
        > > > Regarding the IBM PC, it was manufactured over a
        > 6
        > > > year span. There
        > > > were quite a few changes during the production
        > run.
        > > > Hence, there are a
        > > > LOT of them floating about, mostly worth nil,
        > > > especially "B" models. I
        > > > had examples of all of them. The first general
        > > > production run had 16Kb
        > > > (RAM) motherboards; the power supply and rear
        > panels
        > > > were painted
        > > > black; and the 8080 CPU had a bug (shades of the
        > > > much later Pentium).
        > > > THOSE are the coolest and actually valuable
        > PC's.
        > > > The rest?....
        > > >
        > > > An interesting aside: a fellow I know who worked
        > for
        > > > IBM in Australia
        > > > says the power supplies were always blowing
        > > > up....the early ones
        > > > didn't get the power supply quite right.
        > Bill/KA3AIS
        > > >
        > > >
        > > >
        > >
        > >
        > >
        > >
        > >
        > ____________________________________________________
        > > Start your day with Yahoo! - make it your home
        > page
        > > http://www.yahoo.com/r/hs
        > >
        > >
        >
        >




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