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View Full Version : How to load floppy disks into an Altair?



linuxlove
June 8th, 2009, 06:53 PM
No I don't have an Altair, just Altair32. Anyway, I'm just wonder how you load programs from floppy disks into the Altair's memory.

Erik
June 8th, 2009, 07:46 PM
You need a bootstrap loader.

This is a smallish bit of code that tells the computer enough about how to deal with the disk drive that it can then start loading code from there to access the disk.

Sometimes this was flipped in by hand and sometimes it was loaded from paper tape or cassette (after an appropriate loader for those devices was switched in.)

A better solution was to have the bootstrap loader burned into an EPROM making startup a simple matter of executing code at the appropriate address.

Sometimes there was even a "turnkey" card that executed that particular ROM address when power was applied.

Dwight Elvey
June 9th, 2009, 07:12 AM
Hi
If it had a Digital Systems controller, the bootstrap loader was
DMA loaded from disk on reset.
I have one of these on my IMSAI but they were used in many
early S-100 boxes.
I'd guess your box most likely has a EPROM board someplace
with the bootstrap loader.
Dwight

RichCini
June 9th, 2009, 08:32 AM
No I don't have an Altair, just Altair32. Anyway, I'm just wonder how you load programs from floppy disks into the Altair's memory.

Since the Altair32 is my project, I'll answer :-)

There is a 256-byte long bootstrap ROM image in the files directory. Either load it as a binary at $FF00 or configure it to automatically load using the memory configuration dialog box. Then, ON (and/or) RESET, toggle the FF00 address, EXAMINE, set the disk in the drive and click RUN.

That gets the operating system bootstrapped from the disk image (either AltairDOS, CP/M or Disk BASIC). Loading programs after that would depend on the system being run. CP/M is like MS-DOS and programs can be run by just typing the name at the command line. Disk BASIC is a disk-based BASIC interpreter and thus requires either typing in a program or DLOADing a program. I don't have any native AltairDOS programs but there is a command line syntax that's pretty arcane.

All of the docs are on the Altair32 Web site, but there are some hints in the help file that comes with the Altair32.