CP/M 2.2 on an Altair 88-HDSK hard disk

altairsim hdsk.toml

HDBL 2.00
LOADING FROM 0

48K CP/M 2.2b v1.6
For MITS 88-HDSK

A0>DIR

Mike Douglas's CP/M 2.2 for the 88-HDSK (the HDCPM22v16 build for a 48K machine), booted by the HDBL PROM at FC00 — RUN FC00 is the machine file's whole startup, because on a real machine that was EXAMINE FC00 and RUN. HDBL reads the disk's Pack Descriptor Page, loads the boot pages, and jumps into CP/M.

The 88-HDSK "Datakeeper" is not a floppy card. It is an outboard controller (its own 8X300 processor and Pertec drive) that plugs into the Altair through an 88-4PIO at ports A0h–A7h and moves whole 256-byte sectors for you over a command/handshake protocol. The image is one platter: 406 cylinders × 2 sides × 24 sectors × 256 bytes = 4,988,928 bytes.

^E (STOP) takes the keyboard back to the monitor at any point; RUN resumes. ^C belongs to CP/M (it is warm boot) and CP/M gets it.

The files

There is no undo. Drive 0 is mounted read/write because that is what a real machine is, and CP/M writes to A: for anything you create. In a clone git checkout puts the image back; in a copy you were handed, nothing does. Copy it first if you are about to test writes in anger, or add readonly = true to the drive in hdsk.toml.

BOOT.ASM, BIOS.ASM and the original HDBL.ASM — the authoritative sources this was built and verified against — live at deramp.com (Altair hard-disk software and ROMs). They are source rather than product, so they are not shipped here.