It's hard to tell when you're dealing with such an old hardware that is pretty much undocumented. I would assume that if DX4 is not supported, 586 CPus won't work either. In case of AMD the pinout is the same and if you set the multiplier to 3x it behaves like DX4. You could experiment with the jumper and try to put DX4 in there but make sure the board is really outputting 3.3V.

If I were in this situation I would rather try to find another board which is better documented. And of course you can always use DX2 which are fine CPUs. Just don't play Doom in fullscreen 😁. Or use DX1 to turn the computer into a better 386. Nice for playing adventure games.

The question is really what "not supported" actually means. I'd say it's most likely that there simply is no 3.3V support (missing voltage regulator). You can check that for starters as Paar suggests. Other reasons it might not be supported include things like WB cache support - but that's not a show-stopper: WB-capable CPUs generally happily run in WT-mode.

I have a voltage regulating interposer to use 3.3/3.45V CPUs on 5V boards and have found that an Am5x86 (i.e. a WB DX4 with 4x multiplier) works on basically any board with 486 socket. So if that board actually delivers 3.3V I'd say there's a good chance of a regular DX4 working, just use the basic settings for a 486DX33 if specific settings for DX4 are absent.

Note that the Cx5x86 is a completely different beast and does not work in boards that do not specifically support it.

So if that board actually delivers 3.3V I'd say there's a good chance of a regular DX4 working, just use the basic settings for a 486DX33 if specific settings for DX4 are absent.

Quite a lot of boards use identical or nearly identical jumper settings between DX/DX2 and DX4 WT/DX4 Overdrive.

Paar wrote on 2020-03-06, 06:57:

And of course you can always use DX2 which are fine CPUs. Just don't play Doom in fullscreen 😁.

In fact a DX2 with VL-Bus graphics card can run Doom in fullscreen very close to the max - around 30fps (the framerate is capped at 35fps).

When the DOOM was released in 1993, everybody was talking about early Pentiums, but the DX2-66 was a very high-end CPU and DX4 wasn't even introduced.

How exactly would I determine if I'm getting 3.3V to the CPU?

Look for the Socket pinout. Find Vcc pin and stick a piece of wire in there, then lock the socket. Turn on the motherboard and measure the voltage on the wire (you have to find some ground on the board, for example four middle pins on the power connector). Of coure you have to have a multimeter to do that.

mpe wrote on 2020-03-06, 17:41:

In fact a DX2 with VL-Bus graphics card can run Doom in fullscreen very close to the max - around 30fps (the framerate is capped at 35fps).

I'm little surprised, always thought Doom can run around 25 fps max on DX2. Probably heavily depends on VGA card.

Oh yeah, I have a multimeter but I've never had to do this before so it's a new thing for me. Will have to find some wire then...

In fact a DX2 with VL-Bus graphics card can run Doom in fullscreen very close to the max - around 30fps

No, it doesn't. Some stuff like Doom 2 Downtown on Ultra-violence is quite taxing for DX2.

The Serpent Rider wrote on 2020-03-08, 15:20:

In fact a DX2 with VL-Bus graphics card can run Doom in fullscreen very close to the max - around 30fps

No, it doesn't. Some stuff like Doom 2 Downtown on Ultra-violence is quite taxing for DX2.

This system has PCI, not VL-Bus, so video performance might be slightly faster, but the bonus CPU performance of the DX4 would be nice if it worked.