Yamaha YM2149F audio chip
For Atari ST series (1985)

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 purpose of this page is not the Atari ST itself as we focus only to SOUND and MUSIC applications related to the retro computer world.

ATARI 1040 ST PERSONAL COMPUTER the main panel features a classic keyboard with numeric pad.

Rear panel terminal connectors vary depending on models, these are from 1040STE:
- Midi I/O
- cartridge port
- mouse + joystick inputs
- Modem port (25-dins like RS232) + printer port
- Cinch RCA stereo out
- hard disk input (uncommon proprietary ACSI)
- RF out for low/med resolution
- 13-dins video connector for high resolution + 14-dins floppy disk connector

 

 

OVERVIEW 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:

- high resolution at 640x400 pixels monochrome - medium resolution at 640x200 with 4 colors - low resolution at 320x 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. peek at IC AY38910 click to enlarge

 

THE CHIP 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 digitalized samples (CPU intensive) up to two 8-bit PCM channels which can replay stereo sound at 6,25 / 125 / 25 / 50 kHz.

Audio Xenon game sountrack with YM CHIP + PCM speech sample playback HEAR

ENVELOPE a single 4-segments EG with 8 different preset shapes (4 + 4 inverted) including sawtooth and triangle waveforms.

Although there is no filter structure nor dedicated LFO, many programming tricks allow to create some interesting advanced effects.

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 now we're talking: the Atari St incorporates a standard MIDI I/O and features a very big collections of softwares, some of them still are precious gems even today.

The iconic Midi software is of course the famous CUBASE by Steinberg still updated today on PC/MAC

ATARI OS the OS is called TOS -Tramiel Operating System- (jack Tramiel was the Atari CEO) and installed into the internal ROM, but earlier versions 1.0 needed to be disk-booted.

Latest 520/1040 is 2.06 The graphic interface is the named "GEM" - Graphic Environment Manager. 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 720kb. Today internal drives are considered obsolete and replaced by USB emulators. USB emulator

YM2149F VS EMULATORS today many PC programs emulates the whole ATARI ST systems, including the sounds Paula. Are these so close to the originals? following some comparisons :)

 

RELATED FAMILY:

	ST FAMILY There are many ST models: 520/1040/mega usually followed by letters: ************* M: RF modulator F: built-in floppy E: enhanced (M + F + 4096colors, digisound, hardware scrolling) *************	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
	CUSTOM DIY AY-based synthesizer many projects around like Arduino.	VIDEO
	Commercial product Ay3 by twisted Electrons, a AY-based module synthesizer	VIDEO

 

VIDEO SELECTION Cubase and Midi ST digital audio TRACKING Some game musics

 

GALLERY: