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Thread: fast 486 vs. older Pentium

  1. #1
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    Default fast 486 vs. older Pentium

    Still don't have a working 486 system in my collection, and have noticed that 486 motherboards on eBay have become ridiculously high-priced; I'm guessing because of the retro gaming craze. Apparently there's a lot of retro gamers who insist on authentic period hardware.

    Since early Pentium system boards haven't gotten that expensive, I was considering the possibility of getting one of those instead. Given that later model 486s ran at 66Mz, 80Mz, and faster I was wondering how did they perform compared to an early 60Mz or 90Mz Pentium? Does mainboard cache make much of a difference?

    I already have a tweener that runs a 1Gz AMD Athlon XP cpu. Trying to run MIPS or SI on that gives some ... interesting results, shall we say. Even disabling the cache & kicking the bus speed down I only get it down to 700Mz equivalent, from the vintage utilities I've tried. They weren't made for modern processors. Not much of a gamer here, but a lot of older software (eg MS-DOS applications) don't like speeds that high

    So would a low end Pentium system be an equivalent until I find an affordable 486, or is the generational jump too great? I was thinking of something 200Mz or less.

    Oh, the irony. Back in the early 90s I couldn't wait to dump my 486dx2-66 for a Pentium system. Took me forever to afford one, and a "slow" Pentium MMX 233Mz wasn't fast enough. Now I want them back, and... Heh.

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    A 486DX4-100 would match up fairly evenly with a Pentium-60. Vogons has a couple of lengthy benchmarking threads which might be helpful to you. https://www.vogons.org/viewforum.php?f=46

    This can vary depending on cache. No L2 cache on the Pentium and it might be slower than a equivalently clocked 486 with correctly sized cache.

  3. #3
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    I had a 5x86 133 mhz and that just blew my friend's Pentium 66 away, especially on a pci motherboard

  4. #4

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    A pentium is fine, speed sensitive software usually needs something a lot slower than a 486 to work correctly

    Pentium systems main advantage is floating point,
    “Other “ performance metrics place more modern 486’s on par with Pentium 60-90mhz when floating point isn’t important.
    But the older pentiums should run most anything period correct for a 486

  5. #5
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    Thanks for the link.

    It's been a long time since I studied Pentiums in detail. Would L2 cache be the motherboard cache in the older systems?

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    It sounds like a 75Mz or 90Mz would qualify as a fast 486, then; perhaps like the the 5x86 133Mz that RadRacer203 mentioned...

  7. #7
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    Quote Originally Posted by Casey View Post
    I already have a tweener that runs a 1Gz AMD Athlon XP cpu. Trying to run MIPS or SI on that gives some ... interesting results, shall we say. Even disabling the cache & kicking the bus speed down I only get it down to 700Mz equivalent, from the vintage utilities I've tried. They weren't made for modern processors. Not much of a gamer here, but a lot of older software (eg MS-DOS applications) don't like speeds that high
    Reason that disabling cache on the Athlon XP doesn't reduce performance much is because the architecture wasn't reliant on cache for performance. This is why the Duron with only 64 KB of L2 cache was only about 10% slower than the Athlon at the same speed. That and because it used an exclusive cache design where L1 cache isn't duplicated to L2 cache. If you want more control over speed, get an Athlon XP-M; It's the mobile variant of the Athlon XP and uses the same socket. It has unlocked multipliers and a early version of Cool'n'Quiet (requires a driver under Windows) to dynamically adjust the clock speed, like Intel's Speed Step.

    Intel's Netburst architecture on the other hand was heavily reliant on both large and fast cache for performance. This is why the Netburst Celerons were such pigs, because they had 128-256k of cache until some of the final models based on the Cedar Mill core that got 512k and had respectable performance. Intel was still scummy though, they disabled speed step on Celerons so they consumed a lot more power at all times, and produced more heat. This was a problem on laptops that used the Celeron M (based on the Pentium M), batteries would be quickly drained dry. My Dell laptop I bought in 2006 came with a Celeron 1.5 and the battery lasted exactly 30 minutes. I swapped it out for a Pentium M 2.0 and the battery life jumped to 2.5 hours.

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    I'd say it depends on what you want to run. I always thought Windows 95 ran better on a Socket 5 Pentium than it did on an AMD 133 MHz 486, even on a PCI Socket 3 board. It'd certainly be cheaper, if you had to buy everything anyway.

    The early 60/66 MHz Pentiums were dogs, floating point was broken so you lost one of the big advantages. I'd not bother with one of those.

  9. #9
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    Quote Originally Posted by glitch View Post
    I'd say it depends on what you want to run. I always thought Windows 95 ran better on a Socket 5 Pentium than it did on an AMD 133 MHz 486, even on a PCI Socket 3 board. It'd certainly be cheaper, if you had to buy everything anyway.

    The early 60/66 MHz Pentiums were dogs, floating point was broken so you lost one of the big advantages. I'd not bother with one of those.
    The goal is mostly to simulate a fast 486 environment until I can find a 486 system or motherboard I can afford.

    The mainboard I had at the time came from CompUSA. I had a choice between getting a 486dx2-66 with ISA slots or a 486dx-50 with some VLBus slots. The latter was more expensive, so I went with the dx2-66. It worked quite nicely with 4Mb of ram under DesqView/386. When Win95 came out I bought a Creative Labs sound card/CD-ROM controller. I wasn't about to install '95 on 32 diskettes, or whatever the number was. Increased the ram to 8Mb, and that kept me going for a long time, until I bought a Pentium-90 motherboard, if memory serves. It was a long time ago.

    Basically a system that reproduces a 486 environment and doesn't cause vintage software to blow up. IIRC Turbo Pascal needed a patch when cpu speeds went north of 300Mz. A lot of vintage apps either run far too quickly (being written for 4.77 8088 or 6Mz 286 systems) or just blow up with overflow/underflow errors because the clock checks report impossible results.

    I've seen some socket 3 boards for sale, but more frequently socket 7 boards. I have some ISA vga, network, and sound cards to hand, so that's not too much of a problem. Even have a SB Live! PCI card somewhere.

    P.S. Are there versions of DOSBox that run under XP/98SE? Running that on the 1Gz Athlon is a kludge, but it might be workable.

  10. #10

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    Quote Originally Posted by Casey View Post
    P.S. Are there versions of DOSBox that run under XP/98SE? Running that on the 1Gz Athlon is a kludge, but it might be workable.
    Definitely. I've run a version of DOSBox on a PII 500 under Windows 98. The PII was a bit underpowered but it worked. The Athlon will be fine.
    System 80 Expansion Interface located! Thanks to all who helped out and the good people in the NZ vintage computer forums!

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