WTB imsai or altair - CP/M

This is a discussion on WTB imsai or altair - CP/M ; Wanted dead or alive imsai or altair computers. Email 1975imsai@gmail.com...

+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 20 of 31

Thread: WTB imsai or altair

  1. WTB imsai or altair

    Wanted dead or alive imsai or altair computers.
    Email 1975imsai@gmail.com


  2. Re: WTB imsai or altair

    1975imsai@gmail.com wrote:
    > Wanted dead or alive imsai or altair computers.
    > Email 1975imsai@gmail.com


    Watch Ebay. They pop up there fairly often.

    --
    David Griffith
    dgriffi@cs.csbuak.edu <-- Switch the 'b' and 'u'

  3. Re: WTB imsai or altair

    Yeah LOL but so do the prices.


  4. Re: WTB imsai or altair

    1975imsai@gmail.com wrote:
    >
    > Wanted dead or alive imsai or altair computers.
    > Email 1975imsai@gmail.com

    --------------
    Why does everyone slobber over old S-100 machines, when the S-100
    Bus is the most annoying pig in the world to troubleshoot, a truly
    ****ty design only made necessary by the prematurely release of the
    Intel 8080, a chip that was such a piece of crap that everyone went
    to the 8085 or Z80 the next YEAR to get away from that stupid pig??

    Single board Z-80's were much easier to build and have work, and
    their circuits were simpler and smaller. Put a front panel of an
    Imsai or Altair on one of those, and rip out and toss those stupid
    vicious S-100 card cages and their overly complex boards!

    The S-100 is a design best NOT preserved for posterity!
    -Steve
    --
    -Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
    Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
    http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public

  5. Re: WTB imsai or altair

    R. Steve Walz wrote:
    > 1975imsai@gmail.com wrote:
    >>
    >> Wanted dead or alive imsai or altair computers.
    >> Email 1975imsai@gmail.com

    > --------------
    > Why does everyone slobber over old S-100 machines, when the S-100
    > Bus is the most annoying pig in the world to troubleshoot, a truly
    > ****ty design only made necessary by the prematurely release of the
    > Intel 8080, a chip that was such a piece of crap that everyone went
    > to the 8085 or Z80 the next YEAR to get away from that stupid pig??


    > Single board Z-80's were much easier to build and have work, and
    > their circuits were simpler and smaller. Put a front panel of an
    > Imsai or Altair on one of those, and rip out and toss those stupid
    > vicious S-100 card cages and their overly complex boards!


    To chime in on this, if you want a computer with a front panel; that is
    a good front panel, check http://www.homebrewcpu.org/. Granted these
    machines don't run CP/M, but you can get a front panel that's much more
    interesting. For example, you can directly view and manipulate
    registers. It'll take you a good amount of time, effort, and money; but
    I think it's worthwhile. Someday I'll build one.


    --
    David Griffith
    dgriffi@cs.csbuak.edu <-- Switch the 'b' and 'u'

  6. Re: WTB imsai or altair

    On 2006-01-29, R. Steve Walz wrote:
    > Why does everyone slobber over old S-100 machines, when the S-100
    > Bus is the most annoying pig in the world to troubleshoot, a truly
    > ****ty design only made necessary by the prematurely release of the
    > Intel 8080, a chip that was such a piece of crap that everyone went
    > to the 8085 or Z80 the next YEAR to get away from that stupid pig??


    Because it's historically significant. You don't get as much of a feel for
    just what it was like to run the first generation of personal computers from
    a single-board Z-80.

    History is always worth preserving. I keep my S-100 system running, even
    though I've got a nice shiny P112 to do my CP/M hacking on, just as I keep
    an OS/360 MVT system running on Hercules even though there's newer stuff to
    play with.
    --
    Jay Maynard, K5ZC http://www.conmicro.cx
    http://jmaynard.livejournal.com http://www.tronguy.net
    http://www.hercules-390.org (Yes, that's me!)
    Buy Hercules stuff at http://www.cafepress.com/hercules-390

  7. Re: WTB imsai or altair

    On Sun, 29 Jan 2006 07:51:23 GMT, "R. Steve Walz"
    wrote:

    >1975imsai@gmail.com wrote:
    >>
    >> Wanted dead or alive imsai or altair computers.
    >> Email 1975imsai@gmail.com

    >--------------
    >Why does everyone slobber over old S-100 machines, when the S-100
    >Bus is the most annoying pig in the world to troubleshoot, a truly
    >****ty design only made necessary by the prematurely release of the
    >Intel 8080, a chip that was such a piece of crap that everyone went
    >to the 8085 or Z80 the next YEAR to get away from that stupid pig??
    >
    >Single board Z-80's were much easier to build and have work, and
    >their circuits were simpler and smaller. Put a front panel of an
    >Imsai or Altair on one of those, and rip out and toss those stupid
    >vicious S-100 card cages and their overly complex boards!
    >
    >The S-100 is a design best NOT preserved for posterity!
    >-Steve


    Steve,

    First I agree. The S100 bus was at best a poor design and really was
    married to the 8080. It was also one major pain to do things like DMA
    on. The only worse offense is the PC-XT bus aka ISA.

    Getting some of the products to run reliabily could be a challenge as
    design quality was all over the map from very good to unacceptably
    poor.

    However, it was historically significant and of the major busses it
    was popular. I can complain about it as I've designed for it and have
    eight machines that are S100 running including two Altairs and two
    Northstar Horizons.


    Allison

  8. Re: WTB imsai or altair

    R. Steve Walz wrote:
    > Why does everyone slobber over old S-100 machines, when the S-100
    > Bus is the most annoying pig in the world to troubleshoot, a truly
    > ****ty design only made necessary by the prematurely release of the
    > Intel 8080, a chip that was such a piece of crap that everyone went
    > to the 8085 or Z80 the next YEAR to get away from that stupid pig??


    Of course the above is argumentive, but the core question is often
    asked.

    It's already been posted that the Altair 8800 and the Imsai 8080 are
    historic machines, so that alone accounts for interest in those
    machines. They were the first of a substantial number of S-100 systems,
    and those systems and others were the start of the personal computer
    revolution. I list about 100 manufacturers of S-100 bus cards
    on my S-100 Web site:

    http://retrotechnology.com/herbs_stuff/s100.html

    It's also been said that the S-100 bus is various degrees of awful. If
    so, it's not much more "awful" than Multibus and STDbus which were
    substantially similar to it. And the IEEE-696 bus, the successor to the
    original S-100 bus, was accepted as an IEEE standard, just as Multibus
    I was. To say the Altair or IMSAI, or its bus and chips and
    architecture, were awful or "crap" simply ignores history: they are
    merely old and consistent with the design and economic issues of their
    time. While it's fair to say the earliest Altair/IMSAI bus and systems
    were not as good as later S-100 and IEEE-696 implementations, it's
    often the case that FIRST systems or products are not as good as later
    models or models made to a standard.

    And as this is the comp.os.cpm newsgroup, for an OS that is over a
    quarter century old, the notion that old, or first, is bad seems
    misplaced.

    Herb Johnson

    Herbert R. Johnson, voice 609-771-1503, New Jersey USA
    web site
    domain mirror
    ** hjohnson@njcc.com and njcc.com/~hjohnson are EXPIRED **
    my email address: hjohnson AAT retrotechnology DOTT com
    if no reply, wait & try: herbjohnson ATT comcast DOTT net
    "Herb's Stuff": old Mac, SGI, 8-inch floppy drives
    S-100 IMSAI Altair computers, docs, by "Dr. S-100"


  9. Re: WTB imsai or altair

    In article ,
    dgriffi@cs.csbuak.edu (Dave Griffith) wrote:

    > R. Steve Walz wrote:
    > > 1975imsai@gmail.com wrote:
    > >>
    > >> Wanted dead or alive imsai or altair computers.
    > >> Email 1975imsai@gmail.com

    > > --------------
    > > Why does everyone slobber over old S-100 machines, when the S-100
    > > Bus is the most annoying pig in the world to troubleshoot, a truly
    > > ****ty design only made necessary by the prematurely release of the
    > > Intel 8080, a chip that was such a piece of crap that everyone went
    > > to the 8085 or Z80 the next YEAR to get away from that stupid pig??

    >
    > > Single board Z-80's were much easier to build and have work, and
    > > their circuits were simpler and smaller. Put a front panel of an
    > > Imsai or Altair on one of those, and rip out and toss those stupid
    > > vicious S-100 card cages and their overly complex boards!

    >
    > To chime in on this, if you want a computer with a front panel; that is
    > a good front panel, check http://www.homebrewcpu.org/. Granted these
    > machines don't run CP/M, but you can get a front panel that's much more
    > interesting. For example, you can directly view and manipulate
    > registers. It'll take you a good amount of time, effort, and money; but
    > I think it's worthwhile. Someday I'll build one.


    Though its still not the same as having an original...

  10. Re: WTB imsai or altair

    Jay Maynard wrote:
    >
    > On 2006-01-29, R. Steve Walz wrote:
    > > Why does everyone slobber over old S-100 machines, when the S-100
    > > Bus is the most annoying pig in the world to troubleshoot, a truly
    > > ****ty design only made necessary by the prematurely release of the
    > > Intel 8080, a chip that was such a piece of crap that everyone went
    > > to the 8085 or Z80 the next YEAR to get away from that stupid pig??

    >
    > Because it's historically significant. You don't get as much of a feel for
    > just what it was like to run the first generation of personal computers from
    > a single-board Z-80.

    --------------------------
    And why not, IF you put a front panel on it? The front panel is an
    entirely separate issue!

    You mean what it was like for it to fail to run and not know why.


    > History is always worth preserving. I keep my S-100 system running, even
    > though I've got a nice shiny P112 to do my CP/M hacking on, just as I keep
    > an OS/360 MVT system running on Hercules even though there's newer stuff to
    > play with.
    > --
    > Jay Maynard, K5ZC http://www.conmicro.cx
    > http://jmaynard.livejournal.com http://www.tronguy.net
    > http://www.hercules-390.org (Yes, that's me!)
    > Buy Hercules stuff at http://www.cafepress.com/hercules-390

    ---------------------------
    Sorry, I just don't see it. Everyone I know who has ever bought a
    used S-100 machine has had constant problems making it run and LESS
    often even KEEPING it running because they never DID GET it running.
    I know of literally DOZENS of these albatrosses that have gotten
    passed around without EVER running well enough to actuallly DO
    anything with them!

    Collecting them for "historical" purposes sounds more like hysterical
    purposes, sort of like collecting all the early "airplanes" that
    DIDN'T FLY BECAUSE THEY COULDN'T FLY!
    -Steve
    --
    -Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
    Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
    http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public

  11. Re: WTB imsai or altair

    Herb Johnson wrote:
    >

    .... snip ...
    >
    > It's also been said that the S-100 bus is various degrees of awful.
    > If so, it's not much more "awful" than Multibus and STDbus which
    > were substantially similar to it. And the IEEE-696 bus, the
    > successor to the original S-100 bus, was accepted as an IEEE
    > standard, just as Multibus I was. To say the Altair or IMSAI, or
    > its bus and chips and architecture, were awful or "crap" simply
    > ignores history: they are merely old and consistent with the
    > design and economic issues of their time. While it's fair to say
    > the earliest Altair/IMSAI bus and systems were not as good as
    > later S-100 and IEEE-696 implementations, it's often the case
    > that FIRST systems or products are not as good as later models
    > or models made to a standard.


    Comparisons with Multibus and Stdbus are odious. They were
    designed, S100 was thrown together. IEEE-696 was an attempt to
    improve S100 in a more or less compatible way. S100 just happened
    to become popular because it appeared and was commercialized. I
    had a much better bus at the same time, but it was for internal use
    and never commercialized. Some comparisons: Use of negative
    logic, suitable for wire-ors. Use of dynamic termination, avoiding
    much noise generation and cross-talk. Location of lines, again
    minimizing cross-talk. Use of ground planes on the backplane. All
    these things were cheap, and a matter of design.

    --
    "The power of the Executive to cast a man into prison without
    formulating any charge known to the law, and particularly to
    deny him the judgement of his peers, is in the highest degree
    odious and is the foundation of all totalitarian government
    whether Nazi or Communist." -- W. Churchill, Nov 21, 1943



  12. Re: WTB imsai or altair

    On Mon, 30 Jan 2006 01:59:39 GMT, "R. Steve Walz"
    wrote:

    >Jay Maynard wrote:
    >>
    >> On 2006-01-29, R. Steve Walz wrote:
    >> > Why does everyone slobber over old S-100 machines, when the S-100
    >> > Bus is the most annoying pig in the world to troubleshoot, a truly
    >> > ****ty design only made necessary by the prematurely release of the
    >> > Intel 8080, a chip that was such a piece of crap that everyone went
    >> > to the 8085 or Z80 the next YEAR to get away from that stupid pig??

    >>
    >> Because it's historically significant. You don't get as much of a feel for
    >> just what it was like to run the first generation of personal computers from
    >> a single-board Z-80.

    >--------------------------
    >And why not, IF you put a front panel on it? The front panel is an
    >entirely separate issue!
    >
    >You mean what it was like for it to fail to run and not know why.
    >
    >
    >> History is always worth preserving. I keep my S-100 system running, even
    >> though I've got a nice shiny P112 to do my CP/M hacking on, just as I keep
    >> an OS/360 MVT system running on Hercules even though there's newer stuff to
    >> play with.
    >> --
    >> Jay Maynard, K5ZC http://www.conmicro.cx
    >> http://jmaynard.livejournal.com http://www.tronguy.net
    >> http://www.hercules-390.org (Yes, that's me!)
    >> Buy Hercules stuff at http://www.cafepress.com/hercules-390

    >---------------------------
    >Sorry, I just don't see it. Everyone I know who has ever bought a
    >used S-100 machine has had constant problems making it run and LESS
    >often even KEEPING it running because they never DID GET it running.
    >I know of literally DOZENS of these albatrosses that have gotten
    >passed around without EVER running well enough to actuallly DO
    >anything with them!


    You have met your first one.

    However to get to that point required understanding the beast and
    knowing where the evil lies and being willing to deal with it.

    Personally if you are going to buy an Altair, you deserve what you
    get and it's not pretty. It one of the few I got early (1975) and
    retired early and have no plans to ever power again. If there was
    one clear thing I can say about the IMSAI is it was one huge
    improvement. However it would be a few years and getting rid of the
    front pannel that significantly improved reliability. That and a
    decent airflow which many didn't get even close to right.

    >Collecting them for "historical" purposes sounds more like hysterical
    >purposes, sort of like collecting all the early "airplanes" that
    >DIDN'T FLY BECAUSE THEY COULDN'T FLY!


    For "historical purposes" is the best answer, like old planes and
    boats don't try to fly it or float it, the failure will destroy the
    investment in a something worth more as a static object.
    Those that do are usually experienced and have done it before
    and know the pot of worms well.

    Allison


  13. Re: WTB imsai or altair

    On 2006-01-30, R. Steve Walz wrote:
    >> Because it's historically significant. You don't get as much of a feel for
    >> just what it was like to run the first generation of personal computers from
    >> a single-board Z-80.

    > And why not, IF you put a front panel on it? The front panel is an
    > entirely separate issue!


    Yup. There's far more to it than just the front panel, just as there's far
    more to the experience of running a 360 than feeding cards into a reader and
    watching printout come out the other end.

    > You mean what it was like for it to fail to run and not know why.


    Funny, mine still runs fine.

    > Sorry, I just don't see it. Everyone I know who has ever bought a
    > used S-100 machine has had constant problems making it run and LESS
    > often even KEEPING it running because they never DID GET it running.


    That was true in the days when S-100 was king, too. They were cantankerous
    systems even in the best of times.

    That does not make them one bit less significant historically.

    > Collecting them for "historical" purposes sounds more like hysterical
    > purposes, sort of like collecting all the early "airplanes" that
    > DIDN'T FLY BECAUSE THEY COULDN'T FLY!


    You obviously don't get it, and I suspect you never will. Me, I'd love to
    get my hands on an old IBM 360, too, just so I could run it. Until then, the
    S-100 box is the oldest system in my datacenter.
    --
    Jay Maynard, K5ZC http://www.conmicro.cx
    http://jmaynard.livejournal.com http://www.tronguy.net
    http://www.hercules-390.org (Yes, that's me!)
    Buy Hercules stuff at http://www.cafepress.com/hercules-390

  14. Re: WTB imsai or altair

    On 2006-01-30, CBFalconer wrote:
    > Comparisons with Multibus and Stdbus are odious. They were
    > designed, S100 was thrown together. IEEE-696 was an attempt to
    > improve S100 in a more or less compatible way. S100 just happened
    > to become popular because it appeared and was commercialized. I
    > had a much better bus at the same time, but it was for internal use
    > and never commercialized.


    Lots of folks did. *yawn*

    Yes, the S-100 was a pain...but it had one big advantage: you could actually
    *get* stuff for it. Kinda like Windows vs. the Mac or Linux these days. If
    it weren't for the S-100, we wouldnt' ahve had the proliferation of apliance
    computers within a few short years, because the idea that people should make
    systems that others could actually supply expansion hardware for was by no
    means a given.
    --
    Jay Maynard, K5ZC http://www.conmicro.cx
    http://jmaynard.livejournal.com http://www.tronguy.net
    http://www.hercules-390.org (Yes, that's me!)
    Buy Hercules stuff at http://www.cafepress.com/hercules-390

  15. Re: WTB imsai or altair

    Lots of S-100 systems were perfectly and absolutely reliable. Put a
    Cromemco or CompuPro CPU card in a shielded motherboard (TEI or
    CompuPro) with 64k of static memory and a floppy controller based on a
    Wester Digital chip (the Tarbell single density controller, or double
    density models subsequent to revision E), and they were fine and
    absolutely reliable.


    R. Steve Walz wrote:
    > 1975imsai@gmail.com wrote:
    >
    >>Wanted dead or alive imsai or altair computers.
    >>Email 1975imsai@gmail.com

    >
    > --------------
    > Why does everyone slobber over old S-100 machines, when the S-100
    > Bus is the most annoying pig in the world to troubleshoot, a truly
    > ****ty design only made necessary by the prematurely release of the
    > Intel 8080, a chip that was such a piece of crap that everyone went
    > to the 8085 or Z80 the next YEAR to get away from that stupid pig??
    >
    > Single board Z-80's were much easier to build and have work, and
    > their circuits were simpler and smaller. Put a front panel of an
    > Imsai or Altair on one of those, and rip out and toss those stupid
    > vicious S-100 card cages and their overly complex boards!
    >
    > The S-100 is a design best NOT preserved for posterity!
    > -Steve


  16. Re: WTB imsai or altair

    CBFalconer wrote:
    > Comparisons with Multibus and Stdbus are odious. They were
    > designed, S100 was thrown together. IEEE-696 was an attempt to
    > improve S100 in a more or less compatible way. S100 just happened
    > to become popular because it appeared and was commercialized.


    History is mostly about what "just happened".

    As for the S-100 bus as "thrown together", one can read accounts by or
    about the Altair 8800 designer for the first instance of what became
    known as the "S-100 bus". I say "first instance" because the SECOND
    version by IMSAI made a number of changes while maintaining some
    compatibility. Subsequent to both MITS and IMSAI, other changes or
    variations were made. The major change was to a 16-bit data path and
    24-bit address with
    better bus mastering, done by Compupro et al and which became the
    IEEE-696 standard.

    I discuss all these on my Web pages: for instance the page linked
    below:

    http://www.retrotechnology.com/herbs_stuff/s100bus.html

    ...gives a number of "S-100 bus" pin lists.

    I posted that the other buses were "substantially similar"; I did not
    say if they were better or worse. General consensus is that the Altair
    bus has more problems, the IMSAI less, major manufacturers like
    Compupro, Cromemco were better still. The IEEE-696 is as reasonable a
    design as Multibus I - in my opinion, and you need not agree. But both
    were IEEE standards which I think speaks independently for quality of
    design. The "attempt to improve" was pretty successful in that many
    products had degrees of 696 compatibility, well before the standard was
    finally approved..

    I see no point in cursing the first S-100 systems merely because better
    ones were made later. Historic value and/or interest is a product of
    many considerations; "first" or "early" are strong considerations in
    most cases. In any event the interest in IMSAI and Altair is a fact
    beyond debate. I get several requests a month for such systems, year
    after year.

    Herb Johnson

    Herbert R. Johnson, voice 609-771-1503, New Jersey USA
    web site
    domain mirror
    ** hjohnson@njcc.com and njcc.com/~hjohnson are EXPIRED **
    my email address: hjohnson AAT retrotechnology DOTT com
    if no reply, wait & try: herbjohnson ATT comcast DOTT net
    "Herb's Stuff": old Mac, SGI, 8-inch floppy drives
    S-100 IMSAI Altair computers, docs, by "Dr. S-100"


  17. Re: WTB imsai or altair

    >>Sorry, I just don't see it. Everyone I know who has ever bought a
    >>used S-100 machine has had constant problems making it run and LESS
    >>often even KEEPING it running because they never DID GET it running.
    >>I know of literally DOZENS of these albatrosses that have gotten
    >>passed around without EVER running well enough to actuallly DO
    >>anything with them!


    >You have met your first one.


    And now a second - a quick count shows 15 S-100 machines residing
    in my basement - of these, 14 are currently running, and the last one is
    a big oddball Compuduct machine which was a basket case when I
    got it and I haven't really worked on it much yet (It was physically taken
    apart and many connections removed - including all the wiring for the
    internal monitor).

    I've run into very few "mysterious bus problems", a few of the machines
    needed cleaning of connectors and sockets, and I've had a few caps
    go bad over the years, and even a few bad bits of silicon, but nothing I
    would not expect from 30 year old equipment.


    >Personally if you are going to buy an Altair, you deserve what you
    >get and it's not pretty. It one of the few I got early (1975) and
    >retired early and have no plans to ever power again. If there was
    >one clear thing I can say about the IMSAI is it was one huge
    >improvement. However it would be a few years and getting rid of the
    >front pannel that significantly improved reliability. That and a
    >decent airflow which many didn't get even close to right.


    The Altair was a kit machine, and I think you get a lot of variation
    in the construction. I have two original 1975 Altair 8800's, and both
    are running perfectly.

    One of these is a macine which I have owned since it was almost new
    (late 70's) and it has never let me down. It was my main computing
    platform for quite a few years (many of my early development tools
    began on this machine). Worst problem I've ever had with it is that after
    sitting in box a for quite a few years, I had to clean up the sockets on
    the NorthStar disk controller before it would boot ...

    Another thing that people often forget is that the Altair was the first
    successful commercial "personal computer" - although there were
    other micros before then, this was the first one used by "the masses"
    that defined a standard bus and was popular enough that it got adopted
    by other vendors.

    It was a very simple straightforward design, which consisted mainly of
    taking the signals available on the 8080 CPU and support chips straight
    to the bus connectors. Most of the problems I've seen where people
    complain about the Altair bus are in cases where they have changed the
    CPU to a 4Mhz Z80 - not only does it not match the original 8080 timing,
    but it is being "overclocked" to double it's design speed. Not to mention
    that many of the early Z80 cards (likely to be used in an Altair) were not
    the pinnacle of engineering either...

    Before anyone cries "but the S-100 bus is supposed to be able to do
    this", let me make clear that we are NOT talking about the S-100 bus.
    We are talking about the "Altair bus", also known as the "Roberts bus".

    Mits didn't design the Altair bus to handle S-100 specifications or 4Mhz
    Z80s because nieither of those existed at the time. The S-100 bus grew
    from the Altair implementation. The Altair bus was designed for the Altair,
    which is a 2Mhz 8080 - nothing more, nothing less. The fact that it was
    adopted by so many, and grew to encompass systems far beyond
    the original design is a testiment to the fact that Mits openly documented
    it and did not complicate it with proprietary "junk".

    Yes - the guys who came even a little bit later did it better - this is what
    is supposed to happen, you learn from observing the problems with
    other designs. And with microcontrollers getting cheap, and Z80s on the
    horizon, it was easy to see that dependance on the 8080 bus was not a
    good thing. In 1975 with the 8080 being the only game in town (and not a
    cheap one at that), this was not so obvious...

    To put things in perspective, the last crop of S-100 machines produced
    looked far more like the Altair than pretty much any later crop if "PC"s
    to the IBM 5150.

    Yeah, I am an Altair fan - my Altair was the first machine I put a diskette
    drive on, and got serious about writing software with - In many ways, the
    Altair launched me into my career, and I have deep attachment to it.
    But I also know what it is, which is a pioneering machine, built without
    the benefit of prior experience to draw on - Yet so many people talk
    about how good the later S-100 machines were in comparison to the
    Mits Altair, but only talk about the original 8800 - never the A or B, which
    were Mits improved designs - and I haven't found one of either yet :-(


    >>Collecting them for "historical" purposes sounds more like hysterical
    >>purposes, sort of like collecting all the early "airplanes" that
    >>DIDN'T FLY BECAUSE THEY COULDN'T FLY!


    But the Altair, even the original 8800 DID fly - I put many thousands of
    hours on one (probably more than I put on my PA-28).


    >For "historical purposes" is the best answer, like old planes and
    >boats don't try to fly it or float it, the failure will destroy the
    >investment in a something worth more as a static object.
    >Those that do are usually experienced and have done it before
    >and know the pot of worms well.


    To buy an old Altair thats been sitting in someones basement and
    expect to turn the switch and boot it up is akin to buying a Model-T
    thats been rusting out behind someones barn and drive it away...
    But like the Model-T when properly restored, the Altair is worth
    running, and worth showing.

    I get lots of people who come to see my collection, and the Altairs are
    always among the most popular. I've taken one of them out to local
    schools to demonstrate the "early years" to the students and it was
    very well received. When a local TV station did a feature on my
    collection, they asked me to "shut up" during the boot sequence so
    that they could feature a closeup of the Altair front panel with all the
    sounds of the machine booting --- More and more we are becoming a
    highly digital society, and the early years of personal computing is
    an important part of that history. Please don't toss it in the trash.


    --
    dave04a@ Collector of classic pre-PC computer systems.
    dunfield. If you have an old 8/16 bit non-PC system in need of a good
    com home, please contact me at email address on the left, or
    via contact link of this web site:
    http://www.parse.com/~ddunfield/museum/index.html


  18. Re: WTB imsai or altair

    On Mon, 30 Jan 2006 19:21:40 GMT,
    Dave.Dunfield@use.techsupport.link.on.my.website (Dave Dunfield)
    wrote:

    >>>Sorry, I just don't see it. Everyone I know who has ever bought a
    >>>used S-100 machine has had constant problems making it run and LESS
    >>>often even KEEPING it running because they never DID GET it running.
    >>>I know of literally DOZENS of these albatrosses that have gotten
    >>>passed around without EVER running well enough to actuallly DO
    >>>anything with them!

    >
    >>You have met your first one.

    >
    >And now a second - a quick count shows 15 S-100 machines residing
    >in my basement - of these, 14 are currently running, and the last one is
    >a big oddball Compuduct machine which was a basket case when I
    >got it and I haven't really worked on it much yet (It was physically taken
    >apart and many connections removed - including all the wiring for the
    >internal monitor).
    >
    >I've run into very few "mysterious bus problems", a few of the machines
    >needed cleaning of connectors and sockets, and I've had a few caps
    >go bad over the years, and even a few bad bits of silicon, but nothing I
    >would not expect from 30 year old equipment.
    >
    >
    >>Personally if you are going to buy an Altair, you deserve what you
    >>get and it's not pretty. It one of the few I got early (1975) and
    >>retired early and have no plans to ever power again. If there was
    >>one clear thing I can say about the IMSAI is it was one huge
    >>improvement. However it would be a few years and getting rid of the
    >>front pannel that significantly improved reliability. That and a
    >>decent airflow which many didn't get even close to right.

    >
    >The Altair was a kit machine, and I think you get a lot of variation
    >in the construction. I have two original 1975 Altair 8800's, and both
    >are running perfectly.


    Mine was in the earliest production lots. Most all of the ECOs were
    required. However the dependence on oneshots was problematic.
    Mine the CPU would go off into space and it was the timing generators
    oneshots misfiring. By the summer of '75 I'd changed the oneshots to
    8224 and system stability was good. However I also had the problem of
    some MITS boards being solder plated edge connectors and the early
    88MCD rams were gold over copper (green gold) problems and by the end
    of it's first year most of the connectors were badly contaminated from
    the Logisland costal climate. New backplane fixed that. I bet if I
    dug it out and verified the PS it would run still.

    On the other hand I have an 8800B-T chock full of all MITS cards CA
    1978 including disk and it runs with no problems at all other than
    occasional dusting inside. The pertec disks are even operational.

    >One of these is a macine which I have owned since it was almost new
    >(late 70's) and it has never let me down. It was my main computing
    >platform for quite a few years (many of my early development tools
    >began on this machine). Worst problem I've ever had with it is that after
    >sitting in box a for quite a few years, I had to clean up the sockets on
    >the NorthStar disk controller before it would boot ...


    NS* was near indestructable. My first one suffered two lightining
    hits. First was direct hit to house TV antenna, fried a lot of the
    house electronics and the secod was a nearly pole hit. Both times I
    replaced tha bad chips and kept on trucking.

    >Another thing that people often forget is that the Altair was the first
    >successful commercial "personal computer" - although there were
    >other micros before then, this was the first one used by "the masses"
    >that defined a standard bus and was popular enough that it got adopted
    >by other vendors.


    Indeed it was and highly copied in many variations.

    >It was a very simple straightforward design, which consisted mainly of
    >taking the signals available on the 8080 CPU and support chips straight
    >to the bus connectors. Most of the problems I've seen where people
    >complain about the Altair bus are in cases where they have changed the
    >CPU to a 4Mhz Z80 - not only does it not match the original 8080 timing,
    >but it is being "overclocked" to double it's design speed. Not to mention
    >that many of the early Z80 cards (likely to be used in an Altair) were not
    >the pinnacle of engineering either...


    Two issues made it twitchy. One was the bundle of wires (8800 and A)
    to the front pannel and the other was the older 4 slot ssegmented
    single sided backplanes. Just replacing the backplane with later
    Altair or wamco parts made that mostly go away.

    One item that plagued S100 as a general thing. There were many ram
    cards of the 8k of 2102 flavor were the inputs to the 2102s were not
    buffered from the bus. Bad design, huge capacitive loading and
    issues with ringing even with 8080 (worse if you had 6-7 of them!).

    >Before anyone cries "but the S-100 bus is supposed to be able to do
    >this", let me make clear that we are NOT talking about the S-100 bus.
    >We are talking about the "Altair bus", also known as the "Roberts bus".
    >
    >Mits didn't design the Altair bus to handle S-100 specifications or 4Mhz
    >Z80s because nieither of those existed at the time. The S-100 bus grew
    >from the Altair implementation. The Altair bus was designed for the Altair,
    >which is a 2Mhz 8080 - nothing more, nothing less. The fact that it was
    >adopted by so many, and grew to encompass systems far beyond
    >the original design is a testiment to the fact that Mits openly documented
    >it and did not complicate it with proprietary "junk".
    >
    >Yes - the guys who came even a little bit later did it better - this is what
    >is supposed to happen, you learn from observing the problems with
    >other designs. And with microcontrollers getting cheap, and Z80s on the
    >horizon, it was easy to see that dependance on the 8080 bus was not a
    >good thing. In 1975 with the 8080 being the only game in town (and not a
    >cheap one at that), this was not so obvious...
    >
    >To put things in perspective, the last crop of S-100 machines produced
    >looked far more like the Altair than pretty much any later crop if "PC"s
    >to the IBM 5150.
    >
    >Yeah, I am an Altair fan - my Altair was the first machine I put a diskette
    >drive on, and got serious about writing software with - In many ways, the
    >Altair launched me into my career, and I have deep attachment to it.
    >But I also know what it is, which is a pioneering machine, built without
    >the benefit of prior experience to draw on - Yet so many people talk
    >about how good the later S-100 machines were in comparison to the
    >Mits Altair, but only talk about the original 8800 - never the A or B, which
    >were Mits improved designs - and I haven't found one of either yet :-(


    It was my first and I'll keep it forever. However the 8800B was a
    robust machine based on a lot of learning.

    >>For "historical purposes" is the best answer, like old planes and
    >>boats don't try to fly it or float it, the failure will destroy the
    >>investment in a something worth more as a static object.
    >>Those that do are usually experienced and have done it before
    >>and know the pot of worms well.

    >
    >To buy an old Altair thats been sitting in someones basement and
    >expect to turn the switch and boot it up is akin to buying a Model-T
    >thats been rusting out behind someones barn and drive it away...
    >But like the Model-T when properly restored, the Altair is worth
    >running, and worth showing.


    More like buying a ramp queen (little to unused aircraft thats sat for
    far too long) and flying it without a good inspection and detailed
    maintenance.

    >I get lots of people who come to see my collection, and the Altairs are
    >always among the most popular. I've taken one of them out to local
    >schools to demonstrate the "early years" to the students and it was
    >very well received. When a local TV station did a feature on my
    >collection, they asked me to "shut up" during the boot sequence so
    >that they could feature a closeup of the Altair front panel with all the
    >sounds of the machine booting --- More and more we are becoming a
    >highly digital society, and the early years of personal computing is
    >an important part of that history. Please don't toss it in the trash.


    My first got pretty ugly from traveling and general use. Then again
    it was a work machine not a hobby toy. Despite its warts it worked,
    it was first, and it held fairly well. For it's time it was no better
    or worse than the infamous 5150 was for it's day though by then it was
    almost 7 years old! In computers thats a lifetime.


    Allison


  19. Re: WTB imsai or altair

    Barry Watzman wrote:
    >
    > Lots of S-100 systems were perfectly and absolutely reliable. Put a
    > Cromemco or CompuPro CPU card in a shielded motherboard (TEI or
    > CompuPro) with 64k of static memory and a floppy controller based on a
    > Wester Digital chip (the Tarbell single density controller, or double
    > density models subsequent to revision E), and they were fine and
    > absolutely reliable.

    -------------------
    I understand that was your experience, Barry, however, it got so bad
    in the early 80's that I finally had to refuse to work on them, they
    were so kludgy and buggy. Not everyone had a decent motherboard or CPU
    board, lots of kinds abounded and the cards were NOT truly
    intercompatible merely because they adhered to the bus standard as it
    was found at that time.

    And it was annoying crap, not so much absolute failure, just failures
    to run reliably for long enough to do business with them, for instance!

    Single board computers were absolutely reliable, so I didn't bother
    with ANY bus again till I built a bus of my own and had NO problem
    with it as long as I didn't try to use an 8080 or anything to DO with
    an 8080 on it! The timing requirements of the 8080 were total crap.
    And the S-100 inherited all those worst features in its bus.

    Thanks,
    -Steve
    --
    -Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
    Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
    http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public


    > R. Steve Walz wrote:
    > > 1975imsai@gmail.com wrote:
    > >
    > >>Wanted dead or alive imsai or altair computers.
    > >>Email 1975imsai@gmail.com

    > >
    > > --------------
    > > Why does everyone slobber over old S-100 machines, when the S-100
    > > Bus is the most annoying pig in the world to troubleshoot, a truly
    > > ****ty design only made necessary by the prematurely release of the
    > > Intel 8080, a chip that was such a piece of crap that everyone went
    > > to the 8085 or Z80 the next YEAR to get away from that stupid pig??
    > >
    > > Single board Z-80's were much easier to build and have work, and
    > > their circuits were simpler and smaller. Put a front panel of an
    > > Imsai or Altair on one of those, and rip out and toss those stupid
    > > vicious S-100 card cages and their overly complex boards!
    > >
    > > The S-100 is a design best NOT preserved for posterity!
    > > -Steve


  20. Re: WTB imsai or altair

    Very good reading thanks guys.



    Http://www.thisoldcomputer.org
    Looking for any Imsai and altair computers and parts. We are just
    getting started.


+ Reply to Thread
Page 1 of 2 1 2 LastLast