Post a good picture of the motherboard. If you cannot get a complete board picture take one looking into the case at the board, and then close ups of the jumpers.
Daewoo owned Leading Edge from 1989 until the late 1995 bankruptcy, the farthest I could go back was to the CPC2300 (but no real info on it either).
added: biggest problem is that was when the Internet was just getting going so many old websites or info are long gone.....specially for Daewoo Teletech Co Ltd that made the computers, is like all info previous to that has vanished.

I will try and get some good pictures. A lot of the board is covered up when installed in the case and the drive cage doesn't appear to be removable. At some point I will have to fully disassemble the machine anyway to clean up some residual corrosion. The PO already snipped the battery off.

Extracted the board and took some pictures. Motherboard, option ROM, and SW2.

Jumper blocks

Ok on a quick look over appears to be same or similar to this: https://theretroweb.com/motherboards/s/dash-c … -486sx-25-33-50
most of the jumpers are numbered same and in same places...

Awesome, that does look exactly the same. Thanks!

Quick question, according to the datasheet, there are two CPU speed options: OSC/1 or OSC/2. It appears that there's a 50Mhz crystal, so I can only run this at 25 or 50, is that correct? I'd need to get a 66Mhz crystal to run the CPU at its rated 33 Mhz.

edit: maybe I should just go ahead and source a 50Mhz CPU instead...

Armitage64 wrote on 2023-03-18, 18:33:

Quick question, according to the datasheet, there are two CPU speed options: OSC/1 or OSC/2. It appears that there's a 50Mhz crystal, so I can only run this at 25 or 50, is that correct? I'd need to get a 66Mhz crystal to run the CPU at its rated 33 Mhz.

edit: maybe I should just go ahead and source a 50Mhz CPU instead...

Is the board working?
indeed a 50MHz crytal oscillator but a DX-33 CPU on the board is very suspicious.

CoffeeOne wrote on 2023-03-18, 19:21:

Is the board working?
indeed a 50MHz crytal oscillator but a DX-33 CPU on the board is very suspicious.

Yes it works as it is currently configured. This configuration is probably not factory, it was someone else's project that I just picked up. I've got it apart right now to remove the corrosion and repair the solder mask around the battery. Once I've got it back together I'll run CheckIt or something to verify, but I assume the DX33 is just running at 25 right now.

Armitage64 wrote on 2023-03-18, 19:46:

CoffeeOne wrote on 2023-03-18, 19:21:

Is the board working?
indeed a 50MHz crytal oscillator but a DX-33 CPU on the board is very suspicious.

Yes it works as it is currently configured. This configuration is probably not factory, it was someone else's project that I just picked up. I've got it apart right now to remove the corrosion and repair the solder mask around the battery. Once I've got it back together I'll run CheckIt or something to verify, but I assume the DX33 is just running at 25 right now.

Agree it is most likely at 25Mhz. JP4 is OSC/1 or OSC/2 and set at OSC/2 so 50Mhz/2=25Mhz. The 74f74 next to JP4 is a dual flip-flop which is most likely being used to divide the Xtal to CPU when jumped OSC/2 and bypassed when jumped OSC/1...
If you change the Xtal to a 33Mhz then you would set JP4 to OSC/1 and change JP3 to ATclk/4 instead of /6 to keep an 8Mhz ISA bus..just MHO 😀

Say I wanted to upgrade the machine to the full 50Mhz. Should I just source a DX/50 and reconfigure the board or would a DX2/50 be an okay solution leaving the clock divider in place? I have read that the DX/50 had some issues and this board isn't that advanced.

Speaking of which, any ideas if it would be possible to upgrade the BIOS on this thing so I could at least have HDD geometry auto-detection?