Oh, and how would one obtain a Mr. Bios set up? If you don't mind.

Are they all Um82C481 / Um82C482?
Maybe the one without the sticker is AWARD? For AWARD BIOSes, I can modify the BIOS (and motherboard) to work with a PS/2 mouse.

I have an image of the MR. BIOS for the UMC 481/482. I can send it to you when you're ready for it. I don't recall where I found it anymore. You will need an EEPROM flash BIOS chip though. If your BIOS chips are like the one in that first photo, that is, having a little window on the top, they are not electronically eraseable. They are erased with UV light (the intensity and duration to erase, I am not certain). First see if any of your boards have an EEPROM. You can determine this from the chip's part number and using google search for datasheets.

The three that I have out testing traces on (light scratches, all tested good {bottom side of board}) all have the same chipset numbers. I will check the rest tomorrow, gotta take them out of the box (yes, properly packaged 🤣). However, they are from the same batch. Meaning, you can count each one ascending and descending based off of the serial numbers. I'm guessing they were all bought in bulk for the college in the early 90's. The boards are dated with 93, 4.

http://www.datasheetarchive.com/dl/Scans-067/ … 2IH00218654.pdf

That is all I'm coming up with, it does mention both Um82C481 / Um82C482, but the document is labeled as Um82C480 chipset 386/486 with a date of 1991.

Interesting - what is the auxillary keyboard header for (KB2)?
How many different styles of this motherboard layout do you have?

The EPROM/EEPROM is the chip with the AMI BIOS sticker on it. You need the part number from that to determine if it is an EPROM (UV) or EEPROM.

You have found the UMC chipset datasheet. Apparently, this chipset supports 1024K of interleaved L2 cache and 64 MB of RAM. The motherboard would need to be heavily modified to make 1024K viable.

No exactly sure what you mean by the keyboard header (even googled it) my apologies, it is a AT style keyboard port, which I'm sure you already know.
I was surprised by the datasheet, seems like this is a pretty nice board for the time. What kind of modifications are we talking here? Also, what is viable as far as L2 cache....aaaaaaaaaaaand can I run at least Doom and or carmageddon? I'm doubtful about carmageddon, but Doom I would hope so. Again, this isn't all about games. I am more interested in showcasing this boards ability to be a powerhouse in any way I can.

I will search the BIOS chip tomorrow and get back with you.

There are 5 or 6 gold pins sticking up vertically on the motherboard, next to the keyboard port. Pins sticking up like this are often called a "header" when some type of external input/output cable is connected to it. The manual posted earlier lists this header as a place to plug in an "auxilary keybaord". I haven't come across this before, but perhaps it allows for connection of some keyboard ports which are not so common, allowing you to use your addball keyboard port on this motherboard.

You can use 256 KB of cache and 32 MB of RAM without any modification.

Did they all come with the batteries removed? This is good, otherwise acid would have surely eaten up much of the traces by now.

DOOM benchmarks at 13.7 fps on this motherboard/chipset with the Ti486SXL CPU and a TSENG Labs ET4000/w32i graphics card. This is about as fast as it gets. When I played DOOM on this motherboard, it did feel faster than 13.7 fps though. It seems playeable. Wolfenstein 3D is also very playeable. Carmagedeon? I think not.

If any of this CHIPS have a hallow circular window on top, then you won't be able to reprogram those BIOSes without having access to a UV light source.

Oh yes silly me. I know what a header is (brain fart). I removed the batteries immediately. Luckily the worst damage was just left over plastic from the old battery. There are only 2-4 boards with any kind of tiny micro spots or light discoloration in the traces. The rest are clean, and all traces in those areas have been cleaned and tested good!

So I took a look, and judging by what I felt, all of my BIOS chips have that little window on them. I'll just have to locate and purchase a flashable chip.

x_86 wrote:

tayyare wrote:

It is definitely NOT a dual CPU board. It only has support for two different types of 386 CPU packaging. This is quite advantageous (if your BIOS supports it), since it will allow you to upgrade the system with 486DLC class CPUs or even (I don't know why, but well..) something like Intel RapidCAD.

I'm not too familiar with the Intel RapidCAd. I did some looking around and I understand where it has its gains, but in comparison doesn't seem worth picking up. Am I right on my assumption? We would like the pc to display game capabilities along with more advance programs like CAD, just for computer science education purposes ^___^. A number of these boards are to be made functional again to be interactive with computer science students, we're trying to make a PC history room at the school.

Math coprocessors was utilized (and sometimes required) only by CAD software and compilers like FORTRAN (this was actually why I had one in my 386SX in 1992) during the times, as far as I remember. There were no "3D" yet, and games requiring an FPU was unheard of. Any other software would not even use an FPU even it was installed.

Actually I was asking "why someone would put that in an 386" but If you really want to show some CAD programs in your 386, I would definitely put a math coprocessor (FPU), at least, if (absolutely) not a RapidCAD. Common FPUs are not expensive, and when it comes to CAD or FORTRAN, they really really make their worth.

RapidCAD would be a bit of an extreme (especially while the only available one in ebay going for 120 USD), but in my opinion, would be very cool as well. 🤣 It is different than any 386 or 486DLC CPU/FPU combination, because a RapidCAD FPU is just a dummy chip, since the real FPU is integrated into the CPU, just like it was in 486 CPUs. As far as I know, RapidCAD is the only 386 class CPU with an integrated FPU unit.

Awesome info, so what you're saying is, 486 chips for my board "don't" have a FPU built in? And only the RapidCAD chip had an FPU built in?

feipoa wrote:

Do you have photos of the other 7 boards you got ahold of?.

Here are 5 out of the 7 (thought to be 8 ) boards that I have. I'll post the other down below wince I'm maxed at 5 attachments.

feipoa wrote:

Do you have photos of the other 7 boards you got ahold of?.

Here are the other 2.

Just to mention, although the EEPROM chips require a UV lamp to erase the contents immediately, it merely takes longer without one. So those with their labels removed will lose their contents if exposed to sunlight over a period of time. A programmer will then be required to write the contents again.

Thank you. I couldn't help but notice that the cache installed on these boards is all over the place.

All of these boards are identical, with the exception of the chipset production dates.

Yes, all cache chips are -20's, so from what I understand that allows my am386 to run at 40MHz. Luckily I have enough to make a full set. Also, the only thing not shown in the photo's are the serial number tags located on the side of the last ISA slot.

x_86 wrote:

Awesome info, so what you're saying is, 486 chips for my board "don't" have a FPU built in? And only the RapidCAD chip had an FPU built in?

Actually I was saying the exact opposite: starting with (real) 486 CPUs (excluding SX versions), FPU is always integrated in the CPU. It was a separate unit in all 386 class and below CPUs (including 486DLC type 386 upgrade CPUs, but excluding -only- RapidCAD).