The IBM PC/XT Model 286 was something in between th XT and the AT. It is basically a (nearly) PC/AT type computer in a PC/XT type case. It was produced for a rather short period, perhaps just until the stock of XT cases and/or the old batch of (buggy) 286 chips ran out. Although the 286 CPU ran at a lower frequency that that of the AT, it is said that it was actually faster for some work loads because it had 0 wait state memory, where the AT had 1 wait state memory.
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Date: 1986
CPU: 80286 @ 6 MHz
RAM: 640 KB