There is none 😀 Maybe if you want to slow things down?

Now that I think about it, I admit that it would indeed be fun to try but regrettably I have non to test. I assume that it would become limited by the ISA bus at some point.

The only non-sound-card-related reason I can see for having ISA slots is if you have a Forte VFX-1 headset.

Those came with an ISA controller board that the headset needs in order to function. (And on top of that, it requires a VESA feature connector-equipped graphics card.)

On this page someone tested a bunch of AGP/PCI/ISA graphics cards on a Athlon XP 2200+.

Trying to choose an ISA video card...

On the bottom of this page there are some more benchmarks on a 486DX4-100Mhz.

Trying to choose an ISA video card...

Very nice to see some real life comparisons.