The Atari ST is a line of home computers from Atari Corporation and the successor to the Atari 8-bit family. The initial ST model, the 520ST, saw limited release in April-June 1985 and was widely available in July.

The Atari ST line of computers were launched in 1985 with the Atari 520ST. It included an 8mhz Motorola 68000 CPU and 512kb RAM. Later models, called STFM, had a built-in floppy disk drive, RF-modulator and had the power supply built into the case. "ST" means Sixteen-Thirtytwo, because of the CPU's 16bit data bus and 32bit internals.

Source: https://www.giantbomb.com/atari-st/3045-13/

Atari 520ST
Released: January 1985
Price : US $599
CPU: Motorola 68000 @ 8MHz
RAM: 512K
Display: 320 X 200 - 16 colors
640 X 200 - 4 colors
640 X 400 - monochrome
Ports: RGB, cartridge, parallel, serial, HD
floppy drive, MIDI (2), joystick, mouse
Storage: external SSDD 360K floppy drive
OS: Atari TOS/GEM