I've done a lot of experimenting with industrial Pentium 4 motherboards with ISA slots. In my experience, these can be versatile retro setups especially for a rapidly changing period from the late 80s to late 90s.

Pentium 4 processors have a lot of throttling options, so they're quite versatile for retro gaming. And paired with a motherboard with ISA slots and DMA support, you can have native ISA sound card support under DOS.

I've got one completed system here based on a 3.4GHz Cedar Mill Pentium 4 processor: Pentium 4 Multi-OS Build Log (DOS/3.11/95/NT4/98/2k/Me/XP) This was an experiment to see how many different operating systems I could cram into a single PC. It ended up being one of my favorite builds and I was surprised at just how versatile it is. I've had it throttled down to 286-12MHz level of performance.

I'm also experimenting with a lower-speed (1.6 or 1.8GHz) Pentium 4 socket 478 setup with triple graphic cards (ISA, PCI and AGP). With the right throttling tools, it's possible to throttle lower speed Pentium 4's down to 386 speeds without relying on OCDM or ACPI throttling (since that can cause issues with some games). Paired with a native 1990s ISA graphics card, you effectively get the equivalent of both a native 1990s VGA speed combined with 386 CPU performance.

And then at the high end, you can cover up to 2000/2001 era performance at 1.6 or 1.8GHz with an AGP card.

Just to show what is possible when throttling Pentium 4 processors, these are some performance comparisons for both my Cedar Mill 3.4GHz LGA775 system and a Northwood 1.6GHz socket 478 setup.

For chart reference:

12x to 17x = Cedar Mill processor multiplier settings
CE = full cache enabled
CD = full cache disabled
L1D = level 1 cache disabled
DS = debug store enabled (P4Tool)
DS + BTS = debug store and branch trace store enabled (P4Tool)

I think it's pretty easy to build one basic system to rule all 90's games, extending into the early 2000's a little bit, and including any 80's games that are not speed sensitive.

You just put together a Socket 370 system with a PIII Tualatin, a nice GeForce card for video, and a Sound Blaster 16 for sound.

If you want to include XP era games as well, that gets a little more difficult because XP era hardware breaks full compatibility with the ISA bus for DOS sound, although you could go the Shponglefan route and use P4 hardware that still has full ISA compatibility. But I'm not the biggest fan of the P4 architecture so I won't be the guy to recommend that.

You know, it would be interesting to see how a dual PIII/Xeon system would handle XP era games. Could you achieve high clocked P4 level performance that way? Not sure how many games can take advantage of multiple CPUs.