1987/91 - The First MS-DOS Atari system to ship was the i8088 "PC-1" in 1987.  It was housed in a Mega ST style case, with a 5.25" FDD at the front.   It came standard with a Green monochrome monitor (12"), an ST Mouse and PC style serial keyboard.

Atari also launched the "ABC" systems and then the PC3, 4 and 5 ranges.  Atari models, especially the second run of ABC systems and PC3's were built to a very high specification.  Where most PC compatibles were housed in generally standard "off the shelf" cases, Atari had begun to design and build their own.  Using high quality components, relatively speaking for PC's at this time, manufacturing costs were high, which didn't help sales.   From the Intel 8088 to the 386SX, Atari PC systems did relatively well in Europe, where most of them were sold.*

*DRAM issues hit Atari PC systems a number of times, and the ST line was always first in-line for memory, while PC systems were delayed and stuck in Taiwan. Memory was expensive in the late 80's, and there were only a handful of manufacturing facilities globally.  Atari had even toyed with the idea of manufacturing RAM chips by building its own facility.