■ The Atari ST machines are a series of personal computer released between 1985 and 1993. About 10 ST models were available during this period. Unlike the rival Commodore Amiga PAULA, the Yamaha audio chip was not developed specifically for the ST and resulted quite dull. In counterpart, the Midi implementation boosted the ATARI as one of the most professional computer for musical applications.
■ the classic ST family is based on a single 16-bits Motorola 68000 CPU clocked at 8 MHz with limited multitasking system, while graphic chipset features 3 video resolutions:
- medium resolution at 640 x200 with 4 colors
- low resolution at 320 x 200 with 16 colors
Generally games uses low and med resolutions while hi-res needs custom monitors, although some third-part VGA interface are available (or make it yourself with DIY schematics).
■ ATARI SOUND the sound processor is the IC YM2149F SSG chip (or POKEY) - Software-controlled Sound Generator + 8 bits DAC Texas instruments 0802. The YM2149 is a quasi-clone of the famous IC AY38910 (spectrum ZX, MSX) originally designed by by General Instruments and definitely less powerful than a simple SID from older generation Commodore 64 SID.
The audio chip manages 1 noise generator + 3 square tone generators with variable width- also each voice has 4096 different pitches, not much other control on single voice but an individual volume control (at 4 bit resolution). Successive ST "E" series implemented some revamped graphics and add an enhanced DMA channel that plays better digitized samples (CPU intensive) up to two 8-bit PCM channels which can replay stereo sound at 6,25 / 125 / 25 / 50 kHz. A single 4-segments EG with 8 different preset shapes (4 + 4 inverted) including saw tooth and triangle waveforms.
Basically all ST family includes the same audio chip. Maybe in the future we will release some more pages dedicated to each model, especially to the FALCON- the last ATARI which has many "new" audio features.
■ SAMPLING the ST does not features internal samplers, but third-part interface were available generally at 8 bits resolution for basic ST with limited memory/storage.
■ MIDI Atari St incorporates a standard MIDI I/O and features a very big collections of software, some of them still are precious gems even today like editors for vintage machines, esoteric midi composers, sequencer like Cubase or Emagic Logic with incredible clock stability compared to modern monsters.
■ ATARI OS the OS is called TOS -Tramiel Operating System- Jjack Tramiel was the Atari CEO) and installed into the internal ROM, but earlier versions 1.0 needed to be disk-booted.
Atari GEM TOS. Latest 520/1040 is 2.06 The graphic interface is the named "GEM" - Graphic Environment Manager.
■ ATARI MEMORY basic 520ST features half-meg while superior model 1040 st doubles RAM.
Enhanced ST"E" models (also MEGAS STE) can be expanded up to 4mb with standard 30 pin simms, while successive TT030 (which also incorporate a faster 030 CPU) can be filled up to 12 mb.
■ STORAGE The custom 8 bits ACSI (Atari Small Computer Interface) allows to use only ATARI Hard disk called "Mega files" typically 20/30 mb and later TT implements more common SCSI or even cheaper IDE with last Falcon generation. Third-part are selling virtual hard disk based on ACSI which uses flash RAM.
Most of Atari users had to deal with the internal disk drive compatible with MS-DOS filesystem. Early ST features a very limited 360 KB model, latest Mega STE reaches 1,44mb high density, but most commons are standard DD 720 KB. Today internal drives are considered obsolete and replaced by USB emulators.