Editing Atari 65XEM

{{Infobox computer
| name         = Atari 65XEM
| image        = 
| caption      = 
| manufacturer = Atari Corporation
| type         = Home Computer / Music Computer (prototype)
| release date = Never released (shown at January 1985 CES)
| discontinued = Cancelled (1985)
| price        = Estimated US$30–50 premium over standard 65XE
| cpu          = MOS Technology 6502C @ 1.79 MHz (NTSC) / 1.77 MHz (PAL)
| memory       = 64 KB RAM, 24 KB ROM (16 KB OS, 8 KB BASIC)
| storage      = External cassette tape, optional 5.25" floppy disk drive
| display      = 320×192 pixels maximum, 16 colours with 16 intensity levels (ANTIC/GTIA)
| sound        = AMY additive synthesizer (64 oscillators, 8 voices, 11 octaves); POKEY (4 voices, retained for compatibility)
| dimensions   = Similar to standard Atari 65XE
| weight       = ≈1.7 kg
| os           = Atari XE OS, Atari BASIC Revision C
| predecessor  = [[Atari 65XE]]
| successor    = None (cancelled)
| model        = 65XEM
}}

The '''Atari 65XEM''' (XE Music) was an unreleased variant of the [[Atari 65XE]] designed as a dedicated music computer. It featured the AMY (Additive Musical sYnthesis) sound chip — a 64-oscillator additive synthesizer developed by Atari — in addition to the standard POKEY sound hardware. First shown publicly at the Winter Consumer Electronics Show (CES) in January 1985, the 65XEM was never commercially produced.

== Background ==

The AMY chip originated within the Sunnyvale Research Lab (SRL) at the original Atari, Inc. Beginning around 1983, the chip was developed as part of a new chipset codenamed "Rainbow" that also included a graphics processor and sprite generator. The Rainbow chipset was initially considered for the Atari Sierra workstation project and was later proposed for inclusion in the [[Atari 520ST]].

When the 16-bit ST line moved forward without AMY, Atari Corporation decided to pair the chip with the existing 8-bit [[Atari 65XE]] platform, creating the 65XEM. The concept was to offer a significantly enhanced audio experience at a modest price premium.

== The AMY Synthesizer Chip ==

AMY was a sophisticated single-chip additive synthesizer with the following capabilities:

* ''64 oscillators'' generating sine waves via ROM lookup tables (16-bit)
* ''8 independent output channels'' — oscillators could be combined in pairs to produce up to 8 simultaneous voices
* ''8 frequency ramp generators'' for smooth frequency and amplitude modulation over time
* ''11 octave range''
* ''Random noise generators'' for percussion, explosions, and other wide-spectrum sounds
* ''Digital sound playback'' via Fast Fourier Transform (FFT) — input samples could be analysed and reproduced using the oscillators, achieving telephone-quality voice at just 2,400 baud of bandwidth

The AMY chip was based on the experimental work of Hal Alles at Bell Labs during the 1970s, which had produced a similar additive synthesis system requiring several racks of equipment (the Alles Machine). AMY's system design was led by Gary Sikorski, with Scott Foster as the main architect. Sam Nicolino designed the hardware, John Palevich and Tom Zimmerman contributed to the software.

The AMY would have represented a dramatic improvement over the POKEY chip's 4-channel square wave capabilities, and was considered superior to the Commodore 64's SID chip for music synthesis applications.

== Specifications ==

The 65XEM shared the standard 65XE architecture with the addition of the AMY chip:

* ''Processor:'' MOS Technology 6502C at 1.79 MHz (NTSC) / 1.77 MHz (PAL)
* ''RAM:'' 64 KB
* ''ROM:'' 24 KB (16 KB OS, 8 KB Atari BASIC Revision C)
* ''Graphics:'' ANTIC, GTIA — 16 graphics modes, maximum 320×192 pixels
* ''Sound:'' AMY chip (8 voices, 64 oscillators, 11 octaves) plus POKEY (4 voices, retained for backward compatibility and I/O)
* ''Co-processors:'' ANTIC, GTIA, POKEY, FREDDIE (memory manager)
* ''I/O:'' Composite video output, cartridge port, expansion port, SIO peripheral port, 2 joystick ports
* ''Keyboard:'' Full-stroke, 57 keys, 5 function keys (Help, Start, Select, Option, Reset)
* ''Power:'' External power supply unit (1A, 5V DC)

== Cancellation ==

The 65XEM was shown at the January 1985 CES alongside the standard 65XE and [[Atari 130XE]]. Atari projected a price premium of US$30–50 over the base 65XE. However, the company's focus rapidly shifted to the new 16-bit [[Atari 520ST|Atari ST]] line, which was also being launched at the same show. The 8-bit product line was deprioritised, and the 65XEM was shelved.

The AMY chip itself never reached full production. The technology was later sold to a third party who attempted to introduce it as a professional synthesizer product, but Atari sued, and the project was permanently abandoned.

== Surviving Prototypes ==

A small number of 65XEM prototypes were built. Some have found their way into private museums and collections, where they remain among the rarest Atari 8-bit machines.

== See Also ==
* [[Atari 65XE]]
* [[Atari 65XEP]]
* [[Atari 130XE]]
* [[Atari 520ST]]

== References ==
* [https://en.wikipedia.org/wiki/Atari_AMY Atari AMY] — Wikipedia
* [https://gury.atari8.info/tech/atari65xem.php Atari 65XEM] — Gury's Atari 8-bit Forever Portal
* [https://www.ithistory.org/db/hardware/atari-corporation/atari-65xem Atari 65XEM] — IT History Society

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