Atari Mega ST (1987)

Features

CPU: Motorola MC 68000 8 mHz
RAM: 1 / 2 / 4 MB
ROM: 192 KB
Text Modes: 40 or 80 chars. x 25 lines (bitmapped graphics)
Graphic Modes: 320 x 200 / 640 x 200 / 640 x 400
Colors: 16 (320 x 200), 4 (640 x 200), monochrome (640 x 400) among 512
Sound: 3 channels, 8 octaves programmable sound generator
I/O Ports: Cardridge, Midi (in, out), Centronics, RS232c, Hard Disk, Floppy disk, RGB, Joystick, mouse
Built In Media: 3.5” 360 KB disk-drive
OS: TOS + GEM

MESS currently supports for the Mega ST both cart dumps and disk images. The former are accepted in .stc format and use the “cartridge” (cart) device; the latter are accepted in .st format and use one of the two floppy drives, “floppydisk1” (flop1) and “floppydisk2” (flop2).

Also notice that the “printer” (prin) and the “serial” (serl) port are emulated as well.

Keyboard

This system requires full keyboard emulation to work correctly. At startup, full keyboard emulation mode is enabled by default. Whilst in full keyboard emulation mode, some key associated functionality may be disabled (like the ESC key for EXIT). The keyboard emulation mode is toggled using the “Scroll Lock” key (by default).

BIOS options

Different versions of the TOS roms are supported. You can switch between them, changing the -bios parameter. At command line,

"-bios 0" or "-bios default" = TOS 1.04 (Rainbow TOS)

"-bios 1" or "-bios tos102" = TOS 1.02 (MEGA TOS)

RAM options

Different RAM configurations are possible for the megast in MESS. You can switch between them, changing the -ramsize parameter. At command line, you simply have to add -ramsize ram_value, where ram_value can assume one of the following values

1m - to emulate a Mega ST 1
2m - to emulate a Mega ST 2
4m (default) - to emulate a Mega ST 4

Known Issues

The emulation of this system is Preliminary.

History and Trivia

The Atari Mega ST was the “professional” version of the Atari STf (i.e. later version of Atari ST with built-in floppy drive).

Atari added the “Blitter”, a custom chip designed to perform quick memory moves and increase display speed. The Mega ST had a small battery to hold time and date and a small fan (except for the Mega ST1).

This computer was especially designed to be the cheapest publishing solution (and it was!).

The Mega ST had a pretty good success and was replaced by the Mega STe and by the TT.

(info from old-computers.com)