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

.

Relevant Pages

  • Re: WTB imsai or altair
    ... >I've run into very few "mysterious bus problems", ... >The Altair was a kit machine, and I think you get a lot of variation ... On the other hand I have an 8800B-T chock full of all MITS cards CA ... >but it is being "overclocked" to double it's design speed. ...
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  • Re: WTB imsai or altair
    ... >> Wanted dead or alive imsai or altair computers. ... >Why does everyone slobber over old S-100 machines, ... >The S-100 is a design best NOT preserved for posterity! ... The S100 bus was at best a poor design and really was ...
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