Altair Owners ...

From: Richard Erlacher <>
Date: Thu Jan 4 17:10:04 2001

So ... you're of the opinion that Altair computers shouldn't have a disk?
MITS built them with a disk, didin't they? I can't imagine how the
dress-panel saying "Altair Hard Disk Controller" got on these boxes. The
box bearing "Altair Floppy Disk Drive" on the front dress panel suggests the
MITS people didn't feel the system was complete without one. I got these
boxes in '81 or so, as they were liquidated from a MITS inventory auction,
and I got a load of transformers as well.

Actually, I do remember quite well what paper tape is/was, having been a
computer professional back when computers occupied whole floors of
buildings, but I don't remember ever seeing paper tape used on a computer.
I don't doubt thta it was, though.

My recollection was that the original Altair had no I/O devices at all. To
me that didn't suggest it was complete without them, but it did suggest it
was a work in progress when it appeared on the mag cover in '75 or whenever.
It's going to take a couple of days for me to get my head around the concept
you seem to project.

I have always thought it was a mistake to refer a computer with
non-MITS-original hardware as an Altair. I kind-of see folks calling it a
FORD if it says FORD on it, even if the engine is from a Chrysler and the
transmission is from a DeSoto.

Please see the comments I've embedded in your reply, quoted below.


----- Original Message -----
From: "Rob Kapteyn" <>
To: <>
Sent: Thursday, January 04, 2001 2:42 PM
Subject: RE: Altair Owners ...

> Richard:
> The historically interesting thing about the ALTAIR has how insanely
> primitive it was when it became the sensation that sparked the PC
> Putting a disk on an ALTAIR is kind of cool, but it misses the point of
> primitive they really were.
I'm sure that was primitive.
> 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.
How were they interfaced?
> 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.
Teletype was a terminal equipment manufacturer. That's why so many
terminals had the Teletype label.
> Not for me, though, I have a surplus, converted Friden Flexowriter, (or
> boat anchor), that we modified to be parallel.
> Do you even know what paper tape is ?
> I think that every ALTAIR had to deal with paper tape at some point.
Did MITS make a paper-tape-specific interface? Did they sell a paper tape
> Magnetic media were too unreliable.
I'm not so sure about that. What I seem to recall is that the interfaces to
the magnetic media that were available for microcomputers were what was
unreliable, since microcomputers were such stepchildren in the mid-'70's.
My employer was the owner of the first IBM '370 in our state. Their tapes
and floppy disks didn's seem to cause much trouble, but they were expensive.
> I have a cute little optical paper tape reader that has a row of 9 LEDs
> a corresponding row of photodiodes.
> It sends data as eight bits in parallel.
> There is a row of little holes in the third position that is normally
> intended to tractor the paper tape through a teletype machine.
> The optical paper tape reader uses this hole as a clock signal for
> handshaking with the ALTAIR through a parallel port.
Did MITS produce a parallel port that was used for that purpose?
The paper tape I dealt with most in the early '70's was that 18-level tape
on 2" wide paper. It was widely used in traffic monitoring devices used to
count axles. I built (yes, I placed the LED's and sensors in a plastic
block located in an aluminum base I machined for that purpose, and patched
an interface to a portable calculator into it so the things could be read
and the data stored in the battery-operated calculator and later downloaded
to a minicomputer). I even built a version that used a "standard" set of
mechanical feelers used for reading paper tape by looking for a connection
through the hole in the tape. As on your optical reader, the feeler that
engaged the sprocket hole on the tape was used for timing.
> To load BASIC, you entered a tiny loader program through the front panel
> switches.
The software I have for the Cromemco TV Dazzler board is on paper tape.
I've seen people toggle in a "dumb" loader for paper tape, then load a
program using the paper tape to load a program smart enough to read the
little DECTAPE on a PDP-8.
> This program just looked for the tape reader's clock bit, delayed a
> 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.
> This loader quickly took control and if everything summed correctly after
> then rest of the tape was read, BASIC was running when you were done.
> 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.
I'm under the impression that the Altair Disk Basic, of which I have a copy,
works the same way.
> I also have a "VDM-1" video display card. We converted an old TV work
> with this.
> After BASIC was loaded, we add a "patch" for this through the front panel
> switches.
> 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
> in and looked at what happened.
> Usually, you went to location 0 and hit "run" to get out of a crash.
> A "nasty" crash was when an loop overwrote your memory.
> This happened fairly often too.
> It was always kind of interesting to look at the patterns that appeared in
> the memory when these crashes occurred.
> 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.
> Maybe just a BASIC stamp chip.
> I never kept up with disk controller technology
> I don't really know what a WD1002 is.
> Are your Altairs original or "B" models ?
I don't own an Altair at all. I bought the 80 boxes I bough back in '80-'81
for a project unrelated to Altairs. The boxes I ordered had no dress-panels
and were, in fact, just the shells for the "Altair Floppy Disk Drive" still
in the plastic wrap as shipped to MITS. The controller boxes and the one
complete Floppy Disk Drive were included with my order of boxes and
transformers, gratis, and not included on the shipping manifest.
> I hate to think that as an "original" Altair owner, I am, myself, a museum
> piece :-)
> I am only 39 years old.
Well, I guess I'm closer to being the "real McCoy" since I was nearly your
age when I acquired these boxes.
> When I listen to the war stories of 80-year-olds, I might think of THEM as
museum pieces.
I hope you value what you can gain from them as much as what you can gain
from your Altair.
> -Rob
> -----Original Message-----
> From: Richard Erlacher []
> Sent: Wednesday, January 03, 2001 6:16 PM
> To:
> Subject: Re: Altair Owners ...
> Yeah ... I've got a copy of that MITS DISK BASIC lying about somewhere,
> though there's no documentation on hand.
> The deal is that (1) with one of my scrap S-100 PCB's hacked into a WD1K
> channel, the Altair can then talk to a WD1002-05 HD/FD Controller, as I'm
> putting in the MITS HDC box, and use that to operate the mix of 5-1/4"
> and floppy disks in the second box. It requires no S-100 FDC of any sort.
> Since BIOS code abounds for the WD controllers, I'd say it's not only a
> cool
> set of hardware, but a slick way to get the OS running if it's not
> and I do have HD drives in the form of a "back-end" driver, for the WD1K
> series, that can be autoloaded on boot if CP/M is already running.
> However, using a parallel port board would be more consisitent with what
> was
> done with the original Altair system: the one with the small desk built
> the table-high rack with a desk extending to one side. It used a parallel
> port sort of thingie to talk to the SMD interface in the HDC box, and
> in turn, talked to the CDC HAWK drive in the top portion of the rack
> pedestal onto which the desktop was fitted.
> I could put in some sort of parallel port thingie, and 8255, or perhaps a
> pair of input ports and a pair of output ports, to provide the bits
> necessary to do the job. The channel interface is a lot slicker and
> faster,
> though, and TTL will drive the cable a lot better than an 8255.
> Either one will work, but I've no "feel" for what would be preferred by
> typical Altair owner. Of course I'm particularly interested in placing
> this
> stuff with someone to whom an Altair isn't an Altair if any of the
> doesn't say MITS on it, though only the boxes in this set are original
> Dick
> ----- Original Message -----
> From: "ajp166" <>
> To: <>
> Sent: Wednesday, January 03, 2001 4:52 PM
> Subject: Re: Altair Owners ...
> > From: Rob Kapteyn <>
> >
> >
> > >Hey wait a minute ...
> > >A BIOS on an Altair ?
> > >
> > >Sure there were add-ons (years later) that did this, but if you really
> > want authenticity this is what we did --
> > >
> > >I always had to "boot" my Altair with a simple paper tape loader
> > entered from the switches on
> > >front panel. I did this so many times, I had the 30 octal codes
> > memorized.
> >
> >
> > Often several times until it read the cassette correctly! Saving stuff
> > was easy though bets were
> > off if you could read it later.
> >
> > First homebrew board 8223 (x2 for 64 bytes plus 2 7489s for 16bytes of
> > scratch ram) prom boot!
> >
> > >Once I had Altair BASIC loaded, I generally kept the machine powered up
> > as long as possible.
> >
> >
> > Or until it crashed!
> >
> > >I never knew anyone who actually had a actual floppy for their Altair.
> > >I seem to remember that they cost more than the computer itself, and
> > computer was quite >expensive --($2,000 1974 dollars).
> >
> >
> > I built and debugged two of them for others.
> >
> > Allison
> >
> >
Received on Thu Jan 04 2001 - 17:10:04 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:33:46 BST