The 65XEP was the first portable computer Atari designed. It was first exhibited in 1985, at the CES show. With the 65XEP, Atari intended to compete with the Commodore SX-64
It was actually a portable version of the Atari 65XE including a 3.5" 360 KB disk drive, a 5" green CRT and a battery pack.
The price was fixed at less than $400, but Atari never released this machine. Apparently only one prototype was built.
At the same time, Atari announced a second variation of the 65XE, the 65XEM (for XE Music). This version featured a new powerful polyphonic sound chip called AMY with 8 independent sound voices and 64 oscillators. It was able to synthesize voice and any musical instrument sound much better than the Commodore 64's SID chip.
However, the AMY chip never reached production, so the 65XEM never passed the prototype stage either.
About the AMY soundchip, Malcolm Ramage adds:
While the XEM was the only machine announced that (Should have) used the AMY soundchip, early design notes for the Atari ST also mention the chip. Using AMY in the ST, and the XEM were dropped due to a small problem, nobody knew how to program the chip!
When Jack Trammiel took over Atari, he cut the staff down to around 500, getting rid of the old research and design teams and replacing them with many of the designers he trusted who came with him from Commodore. All the machines already in development were cancelled, including the Sierra project, from which the AMY chip came from. While demo;s of the chip in action were played when the XEM was shown, these were tests done before Atari was sold.
Without the knowledge to use AMY, this advanced sound system was doomed to stay in the research labs forever.
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