For me, when I think 486 system, I'm thinking something like a 486dx2 66, 8meg ram, Soundblaster 16, Diamond VLB video card and a 4x/8x CDROM. That's the nostalgia sweet spot for me.

I would pick a motherboard and go from there. I like the SiS 471 for VLB-based boards. It is fast and has a datasheet so there is a lot of knowledge about how it works. The UMC 498 is a good VLB chipset as well. Others might like the OPTi 895 or other chipsets.

Any VLB board is compatible with the 486DX2-66 and will be able to take maximum advantage of it. 33 MHz bus operation is trouble-free, too.

Some VLB boards were built without a 3.3V voltage regulator. This means 486DX4 and 5x86 CPUs will require an interposer to operate. That adds cost and might lead you to a 486DX2-66.

Older VLB chipsets do not support operating the CPU's internal cache in write-back mode, so 486DX4, 5x86, and Pentium OverDrive CPUs won't operate fully as they were designed when run in those boards. They will drop to write-through mode for compatibility. This has a minor but measurable performance impact. Some otherwise-good, later VLB boards may not be correctly wired for such operation even when the chipset supports it, and would require modification to do so.

There were at least some boards like Packard Bells where the Pentium OverDrive and external cache can't be used together. So you would watch out for compatibility issues if you choose that CPU. I think an Am5x86 (or Cyrix if you want to go that route) 486 system and a separate Socket 7 Pentium system makes more sense.

I tried a POD 83 for a while and found it to be a little bit unstable at times - I can't remember the scenario but it couldn't run something that a regular 486 in the same motherboard could.

A DX33 or DX2 66 are the classic 486's in my book but DOOM won't run smoothly on those, so I'd go with DX4 or 5x86 for that reason.

POD can have compatibility issues with some boards, especially those from before mid-1995 since Intel changed some specs shortly before releasing that CPU. For that reason many earlier boards that claim to be POD-compatible don't work properly with it, especially in L1 WB mode.

Regarding the other CPUs, the DX2-66 is the "classic" one to pair with VLB. However you may want to go with a DX4 or better if you want the best performance on DOOM and similar action games. A 5x86 is obviously the most powerful one alongside the POD, but that CPU was released so late in the game (when much more powerful Pentiums were already common) that IMHO it's not very representative of the 486 era.

I've 3 486's
DX2/66 VLB, It's my childhood PC and the stereotypical 486.
POD 83 VLB, due to it missing 3.3v, haven't had any issues.
586 133 PCI, my "late" 486

I can't think of any games that work on the faster machines that don't work on the DX2. It's true some of the larger levels in Doom aren't as smooth as the other 2 systems (or my mates ISA only DX4/100 back in the day) DX2/66's
Just about everything works better on my P3 so 486 is only for nostalgic or speed sensitive games with alot of these already broken at 66Mhz, all depends on what your needs are really.

1) With a motherboard that has a voltage regulator, 486DX2 is redundant - DX4 can work at 2x multiplier too while still having an option to work at 100 Mhz.
2) Unless you have a decent VLB video card, not some typical Cirrus Logic 542x kind of trash, your experience will be limiting and tied to VGA (320x200) era mostly. Even Warcraft II will be a slog.

Cx5x86-120 is the ultimate 486 for me.. Failing that a DX33 will do. The inbetweens do nothing for me 😁

Flameboi420 wrote on 2023-09-08, 02:59:

Are there any drawbacks to the faster 486 class CPUs or a POD? and somewhat more importantly to me, how does the POD play with VLB.

I'll echo the other comments about OverDrive processors and potential compatibility.

I've been working on a system with a VLB motherboard that is labeled as being "OverDrive Ready". However, using either a Pentium or 486DX4 OverDrive with the default BIOS results in both RAM issues (parity errors) and loss of L2 cache. I documented some of that in a recent post: Re: What retro activity did you get up to today?

I ended up having to replace the BIOS with a MR BIOS v1.65 in order for both RAM and L2 cache to work properly with the OverDrive processors.

Insofar as performance goes, you're generally either better off with going as fast as possible, or slow down to something like a 486 DX-33 for speed sensitive games. While the DX2-66 is the "classic" 486 in a lot of ways, there aren't really any games that benefit from that specific processor. It's either too fast for speed sensitive games or games that need higher performance will benefit from an even faster processor.

The Serpent Rider wrote on 2023-09-08, 12:28:

2) Unless you have a decent VLB video card, not some typical Cirrus Logic 542x kind of trash, your experience will be limiting and tied to VGA (320x200) era mostly. Even Warcraft II will be a slog.

Uh oh. I just got a Cirrus Logic 5428 based VLB card for my build. I was under the impression they were pretty OK. Not the best, but not the worst either.

I actually also pulled the trigger on a 486 build lately. It's the last machine I'm nostalgic for, being my families first computer, and I've been fighting the impulse to do it for years. Finally won an auction for a price I thought was reasonable on a 486 VLB motherboard. 5V only, so I'm going with a DX2 processor and 8 MB of ram. Still waiting on parts to show up, but I got a generic VLB multi IO card and the aforementioned Cirrus Logic VGA card. Still making up my mind on sound cards. Debating between an SB16 CT2800 as I've had good luck with them in other builds, or branching out to an ES1868.

Namrok wrote on 2023-09-08, 13:30:

The Serpent Rider wrote on 2023-09-08, 12:28:

2) Unless you have a decent VLB video card, not some typical Cirrus Logic 542x kind of trash, your experience will be limiting and tied to VGA (320x200) era mostly. Even Warcraft II will be a slog.

Uh oh. I just got a Cirrus Logic 5428 based VLB card for my build. I was under the impression they were pretty OK. Not the best, but not the worst either.

It's a perfectly fine card. Not the fastest, but not terrible either.

I have a couple of them. I have noticed that there is a slight performance difference between them, which I suspect might be related to different memory used on each.

The Serpent Rider wrote on 2023-09-08, 12:28:

2) Unless you have a decent VLB video card, not some typical Cirrus Logic 542x kind of trash, your experience will be limiting and tied to VGA (320x200) era mostly. Even Warcraft II will be a slog.

Never had any performance, stability or compatibility issues with cirrus logic cards. At least not with cards using the PCI or ISA bus. In fact some of my favorite PCI cards are from the CD542x/544x line. What made you dislike them?

Calling the CL-GD542x "trash" is a bit of a hyperbole.

https://dependency-injection.com/vlb-vga-group-test/

It sits comfortably in the middle of the pack and not a significant margin off the peak.

Its Windows acceleration won't light the world on fire but it is up there with the rest of them at color depths you would actually use a 486.

CL-GD542x is a perfectly fine, even good I dareasy, VLB SVGA card.

appiah4 wrote:

Calling the CL-GD542x "trash" is a bit of a hyperbole.

Like I said, limited to VGA. Second graph shows it perfectly. For DX2-66, that's fine, because it can't run VESA games sufficiently fast anyway.

Namrok wrote on 2023-09-08, 13:30:

Uh oh. I just got a Cirrus Logic 5428 based VLB card for my build. I was under the impression they were pretty OK. Not the best, but not the worst either.

I actually also pulled the trigger on a 486 build lately. It's the last machine I'm nostalgic for, being my families first computer, and I've been fighting the impulse to do it for years. Finally won an auction for a price I thought was reasonable on a 486 VLB motherboard. 5V only, so I'm going with a DX2 processor and 8 MB of ram. Still waiting on parts to show up, but I got a generic VLB multi IO card and the aforementioned Cirrus Logic VGA card. Still making up my mind on sound cards. Debating between an SB16 CT2800 as I've had good luck with them in other builds, or branching out to an ES1868.

CL-GD5428 VLB + 486DX2-66 is a pretty archetypal 486
Another nice thing about the 486DX2-66 is that it is the last CPU where the 486 was at the top of the x86 world as opposed to being a budget Pentium alternative

The Serpent Rider wrote on 2023-09-08, 14:11:

appiah4 wrote:

Calling the CL-GD542x "trash" is a bit of a hyperbole.

Like I said, limited to VGA. Second graph shows it perfectly. For DX2-66, that's fine, because it can't run VESA games sufficiently fast anyway.

What VESA mode games exist where the VLB Video Card is the actual bottleneck and not the Socket 3 CPU itself? I will make an educated guess here and say you won't be able to run Duke3D playably on 640x480 using any VLB card on a DX4-100. Here is a post I once made about running Duke3D in 640x480 VESA Mode where the responses anectodally seem to indicate you need at least a Pentium 100-ish to make that possible even on the PCI bus: Re: Duke3D 640x480 hardware requirements?

To add further anectodal evidence, I remember GD542x being EXTREMELY capable at running Sim City 2000 in VESA mode for example.

That point meing made, I'd also like to point out that the second graph is a UI acceleration test, synthetic, and not gaming related.

What VESA mode games exist where the VLB Video Card is the actual bottleneck and not the Socket 3 CPU itself?

For early 3D games - 320x400 and actually improving performance in 320x200 by switching to VESA; for 2D games - 640x480. And CL542x also has limitations which hamper performance if you have more than 16Mb of RAM.

Flameboi420 wrote on 2023-09-08, 02:59:

I am looking to build a 486 VLB system and can't quite decide on a CPU, I'm torn between a Pentium overdrive 83, a 486 DX4 100, AMDs 5x86 or just a good old fashioned 486 dx2 66. Are there any drawbacks to the faster 486 class CPUs or a POD? and somewhat more importantly to me, how does the POD play with VLB.

I personally like the Am5x86. When you have a good mainboard (and having not the worst cpu cooler), you have a very good chance to run it at 160MHz, so 4 times 40. Which is really super fast for a 486 system.

I also agree that the Cirrus 542x graphics is sufficient for a DX2-66.
But for the Am5x86 - 160 you might want to have something better (for example Ark1000 based card), you have big differences in Doom and Wolf3D. Fastest Wolf 3D score is more than 150 for me on a 486 (which is of course not relevant when you really want to play it 😁)
On the other hand windows benchmarks @ 1024x768 resolution is not important for me. Even a Am5x86 at 160MHz is struggling with that, Cyrix 5x86 or Pentium Overdrive will not be much better.

jakethompson1 wrote on 2023-09-08, 14:31:

CL-GD5428 VLB + 486DX2-66 is a pretty archetypal 486
Another nice thing about the 486DX2-66 is that it is the last CPU where the 486 was at the top of the x86 world as opposed to being a budget Pentium alternative

The 486DX2/66 is just one of those processors that i) it seems like everybody had, ii) if somehow you didn't have one, your friends all did and you kinda wanted one and iii) if you got it early enough in its lifecycle, would last you a fairly long time (e.g. isn't a DX2/66 half-usable in Win98?). Kinda like, say, a C2Q Q6600 15+ years later...

Doesn't mean that it's anything particularly significant for retro purposes, just... that it was a marker in the sand for a certain era of computing.

jakethompson1 wrote on 2023-09-08, 03:37:

I would pick a motherboard and go from there.

[...]

Second that.

Finding 486 CPUs is much easier than working, matching motherboards. Any 486 board can run a DX/2-66 (at worst it will run it at slower clock), the rest need specific voltage and feature support.

Given you're asking this question, you're probably fairly new to this game, and late 486 boards and - more so - CPUs are some of the most fiddly things out there, particularly when paired with VLB. You can do some amazing things with these systems (Am5x86 CPUs running at 3x or even 4x 50MHz...), but expect to descend into wait states, swapping cards in and out and between slots and more arcana if you want that. Far better IMHO to start off with relatively unchallenging 33MHz bus speeds and unchallenging (5V) DX/2 CPU.