Actually it's not an ordinary PC-clone with Atari-badge. All engineering is actually made by Atari themselves.
I have a PC3 and it uses EGA, CGA, Hercules and MDA graphics modes.
It features a 8088-2 CPU with switchable speed 4.77Mhz or 8Mhz. My machine also has a 30MB hard disk and runs GEM-desktop. It is also compatible with ST-mouse and external 3.5" ST-foppy drive. It is also a first Atari PC to feature ISA slots for expandability.