386DX became redundant for everyone soon as AMD developed its Am486 I think.

Anders- wrote:

When introduced the 386SX was the middle option, with the 386DX above and the 286 below.

Yes.
But never at the top.

on a sidenote, did the 386SX stay around longer than its DX counterpart?

Who knows...
As a CPU for regular PCs, probably not - see that Compudyne ad I mentioned earlier: 386DX still in offer, but no 386SX.
However, late 386SX boards were pretty compact, ie. convenient for embedded/industrial/etc. purposes.

Only the later 386SX boards were compact. The early ones were mostly full size baby AT.

appiah4 wrote:

386DX became redundant for everyone soon as AMD developed its Am486 I think.

Not really... the Am486 was still a relatively expensive option, perhaps 10-15% cheaper than an Intel-based machine, but that didn't quite make them competitive with 386DX machines, price-wise. 386DX-40 systems were great bang for the buck.
I don't think AMD's original 486DX/DX2 series were every very popular. In my experience it wasn't until they introduced the 486DX4 that AMD-based 486 systems became a popular option.
Before that, the 386DX-40 was the archetypal AMD machine.

Back then many ads offered "386, 40MHz, Cache" and these buzzwords actually resulted in big sales.
And this mobo is nothing more than the minimum implementation of that 😀

So many computers with mobos like this were sold just because they were, say, 10 bucks less than good DX systems 😀

Back to 1991 I bought my first PC, it was an amd286@16MHz.
At April 1992, I went to USA and had paid US$ 138 for an i386SX@25MHz motherboard. Just for comparison, an AMD386DX40 board was US$ 260 and a motherboard with an i486DX33MHz was close to US$ 800.
Every 1MB 30 pin simm module had cost US$ 30 at that days.
An i387SX@25MHz coprocessor had cost US$ 57

In Brazil, where I live, at that era a computer cost 3 to 4 times the equivalent at USA. It was impractical.

Before you go replacing chips on the motherboard, try this... Google for the AT keyboard pinout if you don't know it off the top of your head.

First, with the power disconnected, use your meter to check for continuity to the +5V rail (PSU connector) on the V+ pin. If you don't get continuity, you're missing power -- bad trace or burned-out fuse, probably.

You should also get something like 1K to 10K resistance to +5V from the Clk and Data pins. If you don't, the pull-up resistor(s) might be missing or you have a damaged trace. Check for continuity of those two to Gnd. It should be (at least nearly) infinite. If not, you've got a short somewhere, or your KBC is fried.

Now power it on and switch to VDC mode. You should get 5V on the V+, and also something close to that on the Clk and Data pins after the initial bus test -- they're open-collector lines that are pulled low (0V) by the two sides when communicating with each other.

After testing all of that, you should have found a problem if there is one. If not, then it's probably fair to suspect a failed KBC.

386 DX 40mhz vs 486 SX 25mhz in DOOM:
https://youtu.be/3fcPxAO1FeU?t=130

Señor Ventura wrote:

386 DX 40mhz vs 486 SX 25mhz in DOOM:
https://youtu.be/3fcPxAO1FeU?t=130

Ahh, ISA vs. VLB graphics...
If the graphics cards were identical (or in non-graphics applications), the 386 might actually win.

Señor Ventura wrote:

386 DX 40mhz vs 486 SX 25mhz in DOOM:
https://youtu.be/3fcPxAO1FeU?t=130

My friends Packard Bell 486sx25 actually ran Duke Nukem 3d slower than my IBM Eduquest 386slc25
And I had sound

He had Oak VGA graphics, I had god knows what SVGA graphics

I have fond memories of the 386-DX40 motherboard/system I had for quite a while. 386's of this speed simply purr along running windows 3.1 and applications of this age.

Hence why I built one for retro gaming 😀 Although this time I've plonked in a whole 16meg of memory in it (was stuck with 2 and then later 8meg on my original DX-40) My original DX-40 was a full size motherboard with 64kb of cache, while my current build uses one of the ultra-slim AT boards shown on this thread.
.