First post, by nathanieltolbert
First thing, I am not 100% certain that this board supports DX4 chips. It does support 3.3V processors because I had a 486DX2-66V from AMD which runs at 3.3V working just fine in the system. The motherboard is an absolute mystery to me. The system is a Techmedia NOS system I found online, and I can furnish pictures of the motherboard. It has a CR2032 battery holder soldered directly into it. I did this, and yes, I know I need to add a resistor to it, but I don't know what value, and I didn't at the time of installing it. The board has integrated Dual IDE and Floppy as well as a Cirrus Logic Video, a CL-GD5428. The system works fine with 3.3V or 5V when setting the jumpers correctly. So here's the strangeness. I took out the DX2-66V chip, and I installed the DX4-100. The jumpers are set for DX/DX2. There is no mention on the silkscreening anywhere that I saw on casual observation for DX4. But I wasn't certain that no marking for it would be an issue. I was under the impression that the bus multiplier was internal to the CPU. So I boot the machine up and it boots, counts up the 16MB of RAM and on the System screen as it loads DOS, I see it lists the Processor as a 486DX2. Strange, I thought, so I let it boot all the way to dos, and then I loaded up Phil's Computer Lab DosBench and ran the Check CPU program. It cannot identify anything about the processor except that it's a 486DX2 and it's running at 67.1 MHz. This was really strange to me because there has always been stepping information and what not. I don't know if I have something configured wrong, or if the board for whatever reason doesn't allow a higher multiplier than two. I can't even find any information about this motherboard online while searching. I know it's rebranded. It's a Markvision Flexboard ver 2.1 h21D? I have a picture of the board, because when I originally ordered the system, the PCB that came with it was dead, and we couldn't get it to work at all. The thought was Battery corrosion that I cannot see, so if anyone wants a project I got a board. 😀 But I digress. If someone can take a look at the board picture and see if there is a jumper setting that is supposed to be set or if anyone can find information about this motherboard, I would be really appreciative. The stunning variety of make and manufacturers of 486 boards and systems is just staggering at times. Also, one more question, when I upload a picture that I take of my parts, which file license do I use? Thank you for taking a look and any suggestions that you may have. I very much appreciate the help.