VLB is a unique aspect of the 486, and you can arguably get more performance out of the VLB version of the same chip over PCI in a 486. VLB was only viable circa the year 1994, though. The PCI side was only just getting started then. There are better performing late PCI cards and game compatibility isn't much worse in general. VLB vs. PCI doesn't really add up to a meaningful difference in performance at the resolutions a 486 will run, though.

ISA graphics are just a sad state of affairs for a 486DX grade machine.

ISA/VLB/PCI? Use what your board supports. Only early 486 boards had just ISA expansions. Later added VLB and latest PCI. You can't miss with PCI cards. They are cheap and planty to choose from. I'd go with S3 (Trio64, Virge, Trio3D) or Matrox - although these are more Pentium era if you're period correct.

So then I suppose I have no need for PCI/ISA 486 motherboards as long as I use 33MHz fsb based 486 processors on my VLB/ISA 486 boards?

VLB boards could support up to 50MHz FSB speed. Depends on the model and chipset. Later VLB boards (with socket 3) added support for 3.3V cpus.

kixs wrote:

VLB boards could support up to 50MHz FSB speed. Depends on the model and chipset. Later VLB boards (with socket 3) added support for 3.3V cpus.

I remember reading that CPUs with a 40MHz FSB have problems with VLB mobos. What can you tell me?

/could/ is the operative term. The 50FSB 486 was murder for some boards, let alone trying to force a video card to run at that. I'm sure some can, but that would've been monsterously high end at the time, and made moot rather quickly because the DX2-66 uses a 33FSB.
Does mean a VLB Pentium was... plausible, I guess, but that's pretty silly.

Pentium boards with VLB has to my knowledge, some bridge chip, in order to make the VLB run.
There is a video on youtube, were the owner finds that it can run on a single stick of 72 pin ram.
Another thing he finds, is that the board is rather slow for a Pentium build.

Then there is another video were the owner of a dx50 system, talks about it as being a challenge
and not really something he would recommend for a 486 build.
He talks about this, as a kind of project. A kind of "can it be build" project.

EDIT:
Pentium VLB:
https://www.youtube.com/watch?v=JXpfIVZ7wsc

50mhz project system:
https://www.youtube.com/watch?v=KvQZ0yigTrk

computergeek92 wrote:

I know it is recommended to use ISA sound cards, but would there be potential problems if using a PCI video card over an ISA or VLB based card? What about using other kinds of PCI based cards in the same system?

In general it doesn't matter for compatibility. The BIOS abstracts away any differences in bus interface, so regardless of whether you use ISA, VLB, PCI, AGP, PCI-e, integrated video, or some kind of proprietary bus, the video card looks the same to the rest of the system.

The only exception is when the chipsets/motherboards themselves are buggy. Eg, I've had a 486 board with both PCI and VLB, where the VLB support was buggy. It didn't work properly when there were other ISA cards installed. There are some Pentium boards with VLB as well, and I've heard that they can be troublesome as well, although I've never used one myself.

Other than that, the compatibility depends mainly on the chipset and BIOS that the videocard uses. Some have better compatibility than others. Eg, ET4000 was very popular (mainly because of its excellent performance), so many games were developed for/with ET4000 cards, and as such that more or less became the de-facto standard for SVGA. It is rare to find software that doesn't work properly on an ET4000. Some cards have some timing issues with hardware scrolling (I believe Matrox is one of them), which makes games like Commander Keen not run smoothly. Etc.
But that doesn't depend on the bus. It's not like an ISA version of the card would work better than a VLB or PCI version of the same card.

computergeek92 wrote:

I remember reading that CPUs with a 40MHz FSB have problems with VLB mobos. What can you tell me?

'It depends'.
The early 486 was only available in 25 and 33 MHz versions. So early motherboards would have chipsets designed only up to 33 MHz. Likewise, early VLB cards would only have been designed/tested up to 33 MHz.
When the 486-50 came along, it became apparent just how much more difficult it was to get the whole motherboard, chipset and all VLB cards to work at 50 MHz.
This is what triggered the DX2-66.
There are motherboards/chipsets and VLB cards that can handle 40 or even 50 MHz, but it was not a standard speed, so you have to carefully select your components. It's basically a form of overclocking.

I personally own a 486 VLB system that is technically a 486DX2-66, but I run it overclocked as a DX2-80, so my chipset and VLB cards (Diamond SpeedStar PRO and a WinBond multi IO card) run at 40 MHz, zero waitstate, and it's been working like a charm for over 2 decades. So yes, it certainly is possible. But there's no guarantees.
Having said that, I use a real Intel DX2-66. I had one of those IBM Blue Lightning 486DX2-80 chips at first, and it didn't work properly on my motherboard. Not because of the 40 MHz FSB, but because it's a slightly different architecture, and my board/BIOS was not properly prepared for this.
I also have a Pentium OverDrive 83 MHz, which also does not work on the motherboard. Again, not because of the CPU, but because the board/BIOS isn't properly prepared for it.
Both chips work fine on other, more modern motherboards.

So you have to be careful, not all '486' CPUs work on all motherboards, and not all motherboards will support all voltages, speed grades etc. And not all VLB cards will be happy to operate over 33 MHz.
Late motherboards are a safer bet, then again, late 486 boards tend to be PCI.