Altair Owners ...

From: ajp166 <ajp166_at_bellatlantic.net>
Date: Fri Jan 5 18:07:39 2001

From: Rob Kapteyn <kapteynr_at_cboe.com>


>The historically interesting thing about the ALTAIR has how insanely
>primitive it was when it became the
>sensation that sparked the PC revolution.


It was actually more advanced than it's immediate predecessor and
many times cheaper than commercial systems based on microprocessors.

>Putting a disk on an ALTAIR is kind of cool, but it misses the point of
how
>primitive they really were.


Not really, disks were the expensive peripheral but the design neither
negated nor favored their presence.

>Yes, parallel logic is much more consistent with the Altair era.
>My keyboard is 8-bit parallel, my paper tape reader is 8-bit parallel.


Not really, people use parallel AND serial as available.

>The only common serial devices were Teletype machines (because of their
>evolution from the telegraph).

>Teletypes were the most common "terminal" in use back then.


Not really save for they could be gotten cheaper. the microcomputer
revolution was not about capability, it was about cost!

In spring of 1975, H1000 terminal, ADM1, VT05 to name a few could
be found. My favorite was SWTP CT1024 board modded for 64Char
by 16 lines and lowercase.

>Do you even know what paper tape is ?
>I think that every ALTAIR had to deal with paper tape at some point.
>Magnetic media were too unreliable.


Irrelevent. I had reliable magtape by the summer of 1975.

>I have a cute little optical paper tape reader that has a row of 9 LEDs
and
>a corresponding row of photodiodes.
>It sends data as eight bits in parallel.


Yep, did that too.

>To load BASIC, you entered a tiny loader program through the front panel
>switches.


Rom was expensive and EPROM even more so but by summer of '75
people were using it to get away from the costly and often flakey front
pannel.

>This program just looked for the tape reader's clock bit, delayed a
little,
>then read the rest of the byte and stored it in memory.
>When you loaded Bill Gate's BASIC, the first data loaded was a more
robust
>checksum loader.


Same as the magtape version.

>By the way, in the beginning, ALTAIR BASIC WAS the "Operating System".
>Through PEEKs and POKEs executed from your BASIC programs, you could
>control all of your hardware.


MITS Programming Package I/II gave you editor, assembler, debugger.

>I also have a "VDM-1" video display card. We converted an old TV work
>with this.


Have that too, used a commercial video monitor (used).

>After BASIC was loaded, we add a "patch" for this through the front
panel
>switches.


PT supplied it.

>That was another interesting thing about the ALTAIR, you could always
take
>control of your computer through the front panel switches.
>There was no "reset" button to hit when your system crashed, your just
went
>in and looked at what happened.


Yes there was! the procedure was STOP, RESET, RUN.

>Usually, you went to location 0 and hit "run" to get out of a crash.


Like I said...

>A "nasty" crash was when an loop overwrote your memory.
>This happened fairly often too.


Usually due to processor mistiming ro plain old noise.

>It was always kind of interesting to look at the patterns that appeared
in
>the memory when these crashes occurred.


Caused by the execution of repeated FFh (RST 7).

>I have always thought that if I wanted to be able to easily "boot" my
>ALTAIR to show it off, I would construct
>a box that would let me load and save my programs to a modern PC through
>this parallel port.


A PROM worked killer in 1975.

>I hate to think that as an "original" Altair owner, I am, myself, a
museum
>piece :-)
>I am only 39 years old.


Really kid... I was 22 when I built the first one.

Allison
Received on Fri Jan 05 2001 - 18:07:39 GMT