Based on my experience, it's very dependent on the actual motherboard... it's not as easy as saying that it's either black or white.
On most motherboards I didn't have any issues with running a Voodoo 3 3000 @ 89 MHz AGP clock. However, there are certain motherboards, as you've encountered yourself, where - for some reason - even slower out-of-spec AGP clocks are unattainable (when using a Voodoo 3).

This particular motherboard has been a terrible headache. It is extremely picky about what you feed it. I've had a lot of fun experimenting with it but it is overall fairly underpowered and I expect will at the end of the day be used as a low-end Pentium 2 with a concentration on older Windows 98 titles and DOS games.

Despite the frustration it brings for some things, it excels at booting very fast which is wonderful when experimenting with system stability and testing different config.sys drivers. So it has its usefulness regardless.

Overclocking stability will often depend on more than just one component. It's not uncommon for individual pieces of hardware to work with an overclock but only in certain combinations.
You may find that your V3 will run @83MHz AGP on another board without any issues. It's also possible it doesn't like that overclock at all. Some models generally handle overclocking better than others but in the end it's down to each individual card how well it works out of spec.

Hard to say becasue I don't have any experience with EX chip set. Only thing I can think is your board doesn't have proper PCI divider even though Voodoo is a AGP card It doesn't use the AGP bus for anything but transfer rates. Anf your PCI bus is running out of spec and causing the voodoo to freeze. ATI and Nvidia cards properly support AGP so maybe thats why they are fine. Just a guess, I'm probably completely wrong.

I've only played with a small handful of LX/EX motherboards, and even with a PII 350 in them (100 FSB) none of them were very stable at 83.

Warlord wrote on 2021-08-24, 09:34:

Hard to say becasue I don't have any experience with EX chip set. Only thing I can think is your board doesn't have proper PCI divider even though Voodoo is a AGP card It doesn't use the AGP bus for anything but transfer rates. Anf your PCI bus is running out of spec and causing the voodoo to freeze. ATI and Nvidia cards properly support AGP so maybe thats why they are fine. Just a guess, I'm probably completely wrong.

The card is certainly using the AGP bus if it has an AGP connector. It just isn't using special AGP features. The AGP slot is independent of the PCI bus.

It must still derive its clock from the FSB though I would think.