Must be that the ALi chipset has poor PCI bus performance or something...

PCI = 33 MHz bus frequency, AGP = much more.

Yeah I'd lean towards either bus contention with other cards or a poor PCI implementation with low bandwidth. A way to test that would be a buffered HDD transfer rate test from say HDTach. If say your UltraDMA/133 drive is only pulling 50MB/s buffered, that's not good.

BTW, an AGP Voodoo card only uses the AGP bus as a double-clocked PCI bus. 66 MHz PCI, basically. It doesn't use AGP 2x or any of the extra AGP features like AGP texturing. There's still the advantage of it not being shared with other devices though, so you really do get a lot more bandwidth for video. This didn't really matter much until like GeForce and Radeon, however.

Yes, voodoo3 just use AGP interface and nothing else... the voodoo4500 is the only PCI card on my test machine, there are also a lapc-i and a sb16+db60xg there, but those are both ISA devices...
I doubt that ALI has a poor pci bus implementation , compared to VIA MVP3 it just rocks (but slightly slower, at least u get stabillity)
perhaps I try to find an 4500/AGP 🤣

PS. The ALI chipset only offers UDMA33 btw, will bench that since the controller is a pci device

did some tests (no hdtach, winNT only)
and I got a combined perfomance of ~15mb/s and cached ~78mb/s ... some tests like 512kb/1MB score ~25mb/s
I think it is allright for the typical onboard controller with a 40GB HD...

UltraDMA/33 shouldn't be able to burst at more than 33MB/s. Strange... You should get yourself a cheap UltraDMA 100/133 card. I only use the onboard controllers on old boards for CDROMs.

Voodoo2/3 drivers are optimized for K6-II/III CPUs (i.e. 3DNow! support). Voodoo4/5 drivers are not.