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" hard
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 already,
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 on
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 that,
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 the
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 hardware
doesn't say MITS on it, though only the boxes in this set are original MITS.
Dick
----- Original Message -----
From: "ajp166" <ajp166_at_bellatlantic.net>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, January 03, 2001 4:52 PM
Subject: Re: Altair Owners ...
> From: Rob Kapteyn <kapteynr_at_cboe.com>
>
>
> >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 program
> 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 the
> computer was quite >expensive --($2,000 1974 dollars).
>
>
> I built and debugged two of them for others.
>
> Allison
>
>
Received on Wed Jan 03 2001 - 18:16:13 GMT