Quite hard to justify two 486's in addition to a P1 (even a late one). Perhaps if you had to have multiple running configurations of sound cards or video cards. Though fitting an earlier Pentium along your P233 isn't much easier, I guess.

As my only pure DOS machine, a fast 486 does everything really well for me. Of course there's some early stuff that's fiddly, some late/SVGA stuff where it runs out of steam.

firage wrote:

Quite hard to justify two 486's in addition to a P1 (even a late one). Perhaps if you had to have multiple running configurations of sound cards or video cards.

As my only pure DOS machine, a fast 486 does everything really well for me. Of course there's some early stuff that's fiddly, some late/SVGA stuff where it runs out of steam.

Yeah but do you even need a pure DOS PC for late DOS games? My MMX Win98SE box runs all DOS games better than DOS does thanks to a software synth, soundfonts and winglide..

Pretty much. For 90's DOS, the two critical performance points I know of are at about 386DX-33 and then 486DX-33. I think almost anything that requires more performance than that would run perfectly fine on a P166 if not faster, and a few games from as early as 1994 can use all that extra power in their SVGA modes.

At this point, you're targeting a really specific set of games with their own optimized build.

appiah4 wrote:

Do the high end 486s have anything going for them that low end Pentiums can not offer?

Most 486s with low voltage CPU support can use a Cyrix Cx5x86. This CPU allows switching from 33 to 66 to 100MHz without opening the case. I think that is a killer feature, but not many people know about that or use such a setup. Instead the AMD 133MHz processor seems to be the popular choice. Also because the 133MHz one is easier to get, and 133 MHz may seem like it trumps the Cyrix's 100 MHz. (For some mysterious reason though I would rather use an intel 486DX4-100 over that AMD, since it feels more like a proper 486 ... oh and a DX4 can run at 66MHz too)

Trying to make some similar decisions... My thoughts though, I don't know why but always thought of the dx2/66 as a sweet spot, some games targetted around it before pentium took over.

Last time I ran a U5SX the doom performance was pretty dang good, it's the lack of the FPU that holds it back for games a bit after that, I suspect what might hold yours back is the Trident 9000, I think you only have to go to a 286-12 before you've got "too much CPU" for one of those things, though for your older stuff it may wall be keeping the brakes on enough to keep it playable. That U5 has some special sauce, some integer benchmarks touch P60 levels.

One advantage to early Pentium hardware, and I'm talking early chipsets with slow P54s, or P5s is that it seems super stable on Win95, like it matches the development systems or something.

BitWrangler wrote:

Last time I ran a U5SX the doom performance was pretty dang good

I assume that is a 33MHz CPU. On a 486 VLB with good memory and cache timings you would get around 19 FPS in Doom, on average, with one level of green border. It does not matter much whether the 33MHz CPU is from Intel, AMD, Cyrix or UMC.
A 486DX-100 is what is needed to keep Doom at its 35 FPS maximum ticrate in most scenes. Again with one level of green border.

BitWrangler wrote:

it's the lack of the FPU that holds it back for games a bit after that

What game that does not require a Pentium anyway needs or even uses the FPU? I don't know a single one.

gerwin wrote:

BitWrangler wrote:

Last time I ran a U5SX the doom performance was pretty dang good

I assume that is a 33MHz CPU. On a 486 VLB with good memory and cache timings you would get around 19 FPS in Doom, on average, with one level of green border. It does not matter much whether the 33MHz CPU is from Intel, AMD, Cyrix or UMC.
A 486DX-100 is what is needed to keep Doom at its 35 FPS maximum ticrate in most scenes. Again with one level of green border.

That's not what this shows... http://www.cpu-museum.de/?m=umc&f=u5sx http://www.cpu-museum.de/?m=Intel&f=80486SX

Right, I see the difference there in the Doom benchmarks. Since I do not own a UMC branded chip for testing I have no benchmarks of my own to compare. Maybe the UMC does have some extra tricks up its sleeve. I would like to see a second opinion on that matter, as I assumed UMC would clone the original intel 486 to be cheaper, not to be faster, Just like Cyrix and AMD.

derSammler wrote:

BitWrangler wrote:

it's the lack of the FPU that holds it back for games a bit after that

What game that does not require a Pentium anyway needs or even uses the FPU? I don't know a single one.

Falcon 3.0 can use an FPU for a greatly enhanced experience.
I used to run it on my 386SX-16 with an FPU.

BitWrangler wrote:

That U5 has some special sauce, some integer benchmarks touch P60 levels.

So I read a little; UMC did actually tweak their 486 core. Interesting, and too bad they did not continue their CPU business with clock doubled versions and beyond.
source:

1(C) UMC 1993,1995 U5S Introduction ..... * Executes frequently used instructions 30% to 48% faster than 486SX processor.

They did make clock doubled versions, but they were produced in extremely small numbers shortly before they stopped making CPUs altogether.

BitWrangler wrote:

Trying to make some similar decisions... My thoughts though, I don't know why but always thought of the dx2/66 as a sweet spot, some games targetted around it before pentium took over.

Probably because the DX2 66 listed as recommended system requirements for quite some time and lasted as the minimum system requirements for even longer even though faster systems were actually getting common.

As someone who grew up with a DX2 66, Still has his DX2 66 and loves his DX2 66 more then his 586 133, I cant think of any reason to have one instead of something faster.
Its a nice system to have to represent the 486 class but as already stated any game that has speed issues on faster PC's will also run to fast on the 66

Koltoroc wrote:

They did make clock doubled versions, but they were produced in extremely small numbers shortly before they stopped making CPUs altogether.

Mostly due to lawsuits with Intel.

gerwin wrote:

So I read a little; UMC did actually tweak their 486 core. Interesting, and too bad they did not continue their CPU business wit […]
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BitWrangler wrote:

That U5 has some special sauce, some integer benchmarks touch P60 levels.

So I read a little; UMC did actually tweak their 486 core. Interesting, and too bad they did not continue their CPU business with clock doubled versions and beyond.
source:

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1(C) UMC 1993,1995 U5S Introduction ..... * Executes frequently used instructions 30% to 48% faster than 486SX processor.

I recently benchmarked a U5SX-33F and it came in between that of an Intel/AMD 486DX-33 and an Intel/AMD 486DX2-66 (in terms of integer performance) - My guess is that it would have run the equivalent speed of an Intel 486DX2-50 but, I didn't have one to compare.
Their 40 MHz CPU apparently ran on par with an Intel/AMD 486DX2-66, which I can believe.

Not that it matters, but your time periods are a little early for these CPUs. The DX4 didn't come out until 1994, so basing that on running 88-92 games doesn't make much sense- they weren't targeted for that, let alone Pentium.

For reference, the Pentium 100 came out right around the same time as DX4 (March 94) so it would have been very expensive. I don't recall seeing Pentium on home PC's commonly until 1996, unless you were buying at the high-end. Games were still targeted to 486 until at least the Quake release...

I switched from Amiga in late 96 and the price/performance sweet spot then was P120/P133.

Anyway, I re-read the OP and you are asking if there is a reason to do 486 instead of Pentium. I would say no- most games were not based on the CPU speed like the early days (DOS booters). I don't know of anything that will only run on a 486 that you couldn't run better on a Pentium.

There seems to be a huge fad around building 486 VLB systems right now. I've noticed that this past year based on how difficult it's been to source parts at reasonable prices. If you look on ebay, you can get full Pentium rigs in AT cases ready to go for under $100, but people want 200 or more for ugly untested 486 machines.

For playing games I would do what Phil did in that 4 in 1 video, super socket 7 rig and just disable cache if you need the slow downs.

Ultimately, we just like retro stuff, so build the 486 anyway 😜

r.cade wrote:

For reference, the Pentium 100 came out right around the same time as DX4 (March 94) so it would have been very expensive. I don't recall seeing Pentium on home PC's commonly until 1996, unless you were buying at the high-end. Games were still targeted to 486 until at least the Quake release...

I was upgrading in late '95 and at that time a P75 motherboard/RAM combo which also required better PCI graphics, cost about 50% more than the UMC chipset motherboard, Cyrix 5x86 and RAM that I bought. The 90 and 100 Pentium CPUs were double price or so, the 120/133 at that time were kind of i7 prices. However, every P75 I've got my hands on since will run at 133 with a half decent heatsink on and 2 of them I got to 150 (2x75) so if I had known that then, I might have gone for the P75. At the time though the prevailing wisdom was that P75s were pretty useless and you may as well stick with a fast 486. A year earlier they were more right though, the binning was tight for the gold cap pentiums and they were lucky to overclock to next speed grade, guess yields weren't great at first. (I think actually they might have used up those dies in the PODPs, hence not much overclock potential in those.)