First post, by Great Hierophant
If you want a perfect, i.e. the most powerful IBM PC AT system ever made, you have to start with the last models. There are three models to the AT, but only the third can operate normally at 8MHz. Here is how the eight slots (all full-length) should be used:
Floppy/Fixed Disk Adapter (16-bit, 2 floppy, 2 half-height hard drives)
16MB ISA Parity Memory Expansion Card (16-bit probably, only 15MB recognized)
Serial/Parallel Adapter (PC BIOS supports maximum of two Serial, three Parallel)
Roland MPU-IPC (true MPU-401 capability w/breakout box)
Sound Blaster 1.0 (for Adlib, Sound Blaster DSP and Game Blaster)
IBM Enhanced Graphics Adapter w/256 KB RAM upgrade (for 640x350x16 graphics)
Hercules Graphics Card Plus (for monochrome text + graphics + third parallel)
As far as drives go, you will need one 1.2MB 5.25" Floppy and one 1.44MB 3.5" Floppy (supported in BIOS, requires non-IBM setup program). There should be room for two hard drives, so you will need two of the 30MB hard drives IBM made available for the late model ATs. Finally, you will need a 80287 math co-processor for the socket rated at 8MHz.
Of course, you will need to attach the right kind of peripherals to this device. The Hercules should ideally be connected to an 5151 Monochrome Display and the EGA to the 5154 Enhanced Color Display. The Roland must be connected to an MT-32, early revision. The Keyboard must be a 101-Enhanced keyboard (use a Model M PS/2 keyboard and the appropriate cable.) The mouse should be a Microsoft Serial Mouse.
For games that do not require a 386 for protected mode or a VGA, this is undoubtedly the most powerful and compatible PC ever made. It should run any of DOS game that does not require either type of hardware. It may not run the game as quickly as you may like. In fact, as the AT has a speed limiter, it won't ever run any faster.