Closest match I could find, which you've mentioned: https://th99.bl4ckb0x.de/m/C-D/31252.htm

The configuration probably is shared between versions.

Its close, I imagine the specs are accurate. I'm just a litter thrown off by some of the features of my board, aaaaaaand the lack of documentation. I have already viewed what you have found, and thank you very much. I'm confused by the extra sockets, and one being labeled as a 80286 socket, the other I'm sure is for a weitek...

I think it is simply a matter of you having version 1 and the link showing version 1.1 so the drawing doesn't match exactly.
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I also suspect that 80286 marking is simply an error. (Not unheard of.)
80286 CPUs only have two rows of pins down each side.
That socket has three rows which is consistent with an 80386.
Also the chipset suggests 386.
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x_86 wrote:

Basically, what do I have, what kind of coprocessor should I pair with it, aaaaand whats my best performance options....?

Weitek is so special that there is next to no support for those, except for some Fortran compilers and some CAD or scientific software.
As for 387 FPUs: There are performance differences between those, but any FPU at all is much faster than none, assuming your programs need or at least support one. (Most games which will run OK on a 386 can't use an FPU.) IIRC Cyrix FPUs are faster than Intel ones, later Cyrix models are a bit slower, IIT is also not bad, don't remember about the others. But mostly you would be installing one just to occupy the socket.
The 486 FPU is superior to any 387.

Thank you everybody for replying so quickly. So, if the other socket is indeed a 80386, does that mean this is some type of dual socket board that probably has next to no support for that feature? The boards came from the college I attend, we're working on a project to restore all of these into functioning pc's to put in a interactive display for computer science students. I'm thinking these will be interesting to document due to their fall out features.

Nice board... and funny typo! I wonder how many people have tried to insert unsuccessfully a 286 in there. 🤣

I have a similar board. Performance wise it should be pretty good... you'll need to run and post your speedsys / memest results.

I'd go with Cyrix for an FPU... though as is, it will run any games from that era.

I will make sure to do that! I'm currently waiting on a power supply adapter cable, floppy disk emulator, and figuring out what I should do case wise. Between the 8 boards I have enough ram and cache chips to max out one board. I also have a Sound Blaster CT4170 card that I'm hoping will work fine with this setup. There are some nice AT cases floating around on ebay as well, buuuuut I could build an air tight wood case with awesome ventilation and air filtration system that should keep these boards lasting a long time.

Also, I've read that this version of the am386 dx-40 can get pretty hot in turbo mode, any remedies or heatsink solutions I should fab up? Just out of curiosity, otherwise I have noooo problems leaving it alone.

x_86 wrote:

Also, I've read that this version of the am386 dx-40 can get pretty hot in turbo mode, any remedies or heatsink solutions I should fab up? Just out of curiosity, otherwise I have noooo problems leaving it alone.

Traditionally 386's ussully run quite hot anyway... it would be more an issue if you did not have another 132 pin PGA socket for another 386, but in this case you do... so if anything happened to the onboard CPU, you could disable and insert a new one.

For folk that don't have a socket option and only the onboard CPU... yes, I would suggest protecting the thing best they could. There are plenty of heatsinks on ebay... i'm sure you'll find one the right size should you decide to get one anyways... it would not hurt!

Preventative maintenance is better than restorative maintenance.

Great info, I'm super excited to get these boards up and running. Much appreciated.

x_86 wrote:

Thank you everybody for replying so quickly. So, if the other socket is indeed a 80386, does that mean this is some type of dual socket board that probably has next to no support for that feature? The boards came from the college I attend, we're working on a project to restore all of these into functioning pc's to put in a interactive display for computer science students. I'm thinking these will be interesting to document due to their fall out features.

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.

Although it will not hurt, CPU cooling was almost unheard of in 386 era, their operating temp rating is quite high, their TDPs are miniscule.

From CPU-World, for your class of embedded CPUs:

Minimum/Maximum operating temperature: 0°C - 100°C
Typical/Maximum power dissipation: 2 Watt / 3.03 Watt

http://www.cpu-world.com/CPUs/80386/AMD-NG80386DX-40.html

So, don't touch it, it will blister your finger (happened to me with my 386SX-16), but will continue to work none the less 🤣

If there is not a jumper to disable the onboard CPU, chances are it would have to be sliced off in order to take advantage of the PGA socket. Usually they leave the PGA socket off the board if the PQFP cpu is present, but sometimes they make mistakes and give you extra parts you can't use.

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

If you are going to build your case out of wood, keep in mind that metal casing is typically used to provide EMI protection. So if you are going to use wood, at least line the inside of the wood with aluminum foil and ground it to the motherboard/PSU's ground.

My UMC-based 386 board has very good bus throughput, although the main memory throughput tested on the low side. Your chipset should support 486DLC and 486SXL CPUs, however as Anonymous Coward noted, you will likely need to cut of your QFP AMD DX40 chip. I had to do this on my UMC-based 386 board.

The good knews is that the board you have is branded by a major motherboard manufacturer, MSI.

feipoa wrote:

If you are going to build your case out of wood, keep in mind that metal casing is typically used to provide EMI protection.

BINGO!
This is also the reason I/O shields are metal and why front bays come with metal knock-outs or covers (behind the plastic covers) for the unused bays.
Properly named it's called a Faraday Cage. https://en.wikipedia.org/wiki/Faraday_cage

feipoa wrote:

So if you are going to use wood, at least line the inside of the wood with aluminum foil and ground it to the motherboard/PSU's ground.

Window screen (so long as it's the metal kind) or 1/8" to 1/4" mesh hardware cloth also works.

If you install it as individual panels then you need to make sure every panel is grounded to adjacent panels at multiple points and to the PSU/Mobo ground. (Also multiple points from the cage.)
If you don't use multiple ground points from the cage you may inadvertently create an antenna which collects EMI and feeds it into your ground plane.

Wooden cases can be WAY WAY cool, but doing one correctly without turning it into an ugly abomination in the process can be a pita.

[ I once dealt with a system in a plastic case in which every time someone nearby used a cell phone the system crashed. ]
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x_86 wrote:

I've been given a stack of am386 dx-40 (soldered chip) boards

Sorry to 'lower the tone' of your post and apologies if this request is unwelcome but how many of these boards do you have and would you be interested in selling one? I'm very interested in acquiring a DX-40 board. Thanks!

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.

feipoa wrote:

Your chipset should support 486DLC and 486SXL CPUs, however as Anonymous Coward noted, you will likely need to cut of your QFP AMD DX40 chip. I had to do this on my UMC-based 386 board.

Do you have a recommendation on either the DLC or SXL, while combining input with the return question I posted to "tayyare" above?

PCBONEZ wrote:

feipoa wrote:

If you are going to build your case out of wood, keep in mind

I will definitely be adding to, or creating a new post when I start work on the case for these boards. They will be cased individually, but maybe you and some others could help clarify that my grounding procedures are correct. Thanks for the input.

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To everyone else who as replied, I can't thank you all enough! I'm open to all suggestions and input, I'll keep posting as I progress with these boards.

Aslo, does anybody think its completely safe to use the at to atx power supply adapters?

I have used the ATX to AT converters on 486s without problem or concern.

I personally think the SXL is more interesting than the DLC because it has 8 KB of L1 cache as opposed to 1 KB. The SXL also has the ability to clock double. I use an SXL in my UMC-based 386 board, which is similar to yours. I am using Mr. BIOS on it, which I recommend you do as well. This is a 3rd-party BIOS (not AMI or AWARD) and is loaded with features, including DLC/SXL cache support, amongst others. Is the BIOS on your boards AMI or AWARD-based? I would be very interested in obtaining BIOS images for all your 386 boards with a UMC chipset.

Here is a brief comparison I did with some 386 motherboards and their chipsets. Not on this list is a VLSI-based board, which performed similar to the SiS 310/320/330.
386 motherboard chipset comparison

Thanks for the input. The bios chip sticker is missing on this board I posted, but all the rest of them state "(c) 1986 AMI, All Rights Reserved, 386 BIOS PLUS, AMI, 025812. I would be more than happy to try an obtain an image off of the chip, and they are all UMC chipsets.