Homemade windows 3.1 computer

SISI = SCSI?
I'd avoid scsi. Older scsi drives are harder to find than PC-standard IDE, plus your install will be more complicated since scsi will require additional - and possibly hard to find - drivers.

Any reason you specifically want 20 MHz? You could get a 386 or 486 at that speed, though if you want PS/2 connections, you'll probably find those on a 486 board.
Dos 6.22/Win 3.1 will be just as happy on a Pentium 1, which might be easier or cheaper to source.

I really can't recommend one motherboard over another, since your choices are limited to what you can find on the used market. The kind of board you decide on will depend on the processor you want, and if you're going with a 486 or later, whether you want ISA, PCI or a board with a bit of both.

By the way, if you want to tinker with Dos/Win3 before deciding on hardware, here is a good guide for setting them up on a modern PC with DosBox.

Mac,

For a Motherboard and Processor just how far back do you want to go?

You can run DOS 6.2 and Windows 3.1 on a 386 DX, a 486 DX, or a first gen Pentium.
I have built several of these myself, but you can buy the package you have outlined off of ebay for little of nothing.

Do you have a case and power supply?
Will the Motherboard you have utilize the power supply, or will you have to match it?
Will you have to go searching for the Chip Set Software online?

As for SCSI versus IDE Hard Drives, you're better off going with IDE. This will give better expandability straight from the Motherboard instead of having to use controller cards for the SCSI Drives.

Good Hunting.

I go through a lot of computers, and have a bunch of junk computers waiting to go to scrap, some are 386/486 (IBM, Compaq and Gateway). If you let me know before they go out, I can hold some back, let you know what they are, and send you the board/whole thing to you for the cost of shipping + 10 for packaging and time. I was not really into non apple stuff at the time, but if I'm remembering right Gateway might have used standard case at the time (AT) I think IBM and Compaq were always 'special'. Around the time 2GB was the max, I'm thinking many drives had a jumper you could set to work under the 2GB limit.

Mac,

I don't have a case but a have a power supply. It's a Antec SL350 350w power supply, Will Windows 3.1 be happy with that?

I don't have a motherboard but if I can get one from you for 20 or so dollars I will be happy.

I don't have any more. I stopped building PC's a while back and started working on Mac's.

I will look for the Chip Set Software online, I like doing that.

Your best bet is to get an older IBM/Intel board with CPU already mounted that you can go to thier sites for thier established Chipset software.

I'd like to look for a CPU on the Internet but I don't have a credit card or a PayPal account.

If you have a bank account; you can set up a Paypal account. I have been doing it for almost 17 years.

Steven

I don't have a case but a have a power supply. It's a Antec SL350 350w power supply, Will Windows 3.1 be happy with that?

350 Watts will be more than enough, but if you want to use that power supply you'll have to make sure the motherboard you choose supports an ATX connector.

Those won't work together. The board is a socket 7 board, which is not what a 486 uses, that was for pentiums. I think that 486 is a socket 3 if I remember right.