CP/M and FDOS on an iCOM FD3712/FD3812 8″ floppy

altairsim cpm22.toml

48K CP/M 2.2 v1.0
for iCOM FD3712 and Altair

A>DIR

These machines have the iCOM FD3712/FD3812 8″ floppy controller. They run CP/M in single density and in double density. They also run both revisions of iCOM's own FDOS disk operating system. Each machine boots when you start it. The startup of each machine file is RUN F000 for CP/M and RUN C000 for FDOS. On a real machine, you did the same: you examined the PROM address and pressed RUN.

The iCOM controller is a command and handshake controller. The Tarbell and VersaFloppy controllers shift bits. The iCOM controller buffers a whole sector instead. The processor moves the bytes through two ports (C0h and C1h). The disk driver of the operating system runs from a boot PROM in high memory: F000 for CP/M and C000 for FDOS.

The single-density FD3712 disk is 77 × 26 × 128 = 256,256 bytes. The double-density FD3812 disk has mixed density. Track 0 is single density. Tracks 1 to 76 are double density. The disk is 509,184 bytes.

Press Ctrl-E (STOP) to go back to the monitor at any time. Type RUN to continue. CP/M gets Ctrl-C, because Ctrl-C is a warm boot in CP/M. The FDOS prompt is !. The two FDOS revisions have different commands. FDOS-III takes word commands: LIST shows the directory. The original FDOS-I takes single-letter directives: L shows the directory, A assembles, and P prints.

The files

The disks have no undo. Drive 0 is mounted read/write, as on a real machine. The guest writes to the disk for each file you create. In a clone, git checkout puts the disk image back. In a copy that you received, nothing does. To test writes, copy the folder first. Or add readonly = true to the drive.

The boot PROMs are Mike Douglas disassemblies. The disk images are from deramp.com (iCOM Floppy Systems). The machines read and write existing disks. They cannot make a blank format. This is the same as the other controllers in this repository. All the disks here are already formatted.