The Atari Mega ST was the "professionnal" version of the Atari STf.
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 photo shows the Mega ST 4 (4 MB) with a monochrome display (640 x 400), the publishing software "Publishing Partner", the Atari SH 205 hard disk (an old 20 MB 5.25" MFM hard disk) and the Atari SLM 804 laser printer. This printer was really cheap because it had no on-board memory and no page description language, the page was created in the Mega ST memory, then sent to the printer.
The Mega ST had a pretty good success and was replaced by the Mega STe and by the TT.
Motorola MC 68000
1 / 2 / 4 MB
40 or 80 chars. x 25 lines (bitmapped graphics)
320 x 200 / 640 x 200 / 640 x 400
16 (320 x 200), 4 (640 x 200), monochrome (640 x 400) among 512