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Thread: P66, POD83, and AM5x86 133 comparison.

  1. #1
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    Default P66, POD83, and AM5x86 133 comparison.

    Made this awhile back and posted it to VOGONS, though it garnered no responses. Just found it again. Nothing hugely detailed, just some scored from Phil's Benchmarking pack. Options 2, 4, 6, B and C were used.
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  2. #2

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    Seems to be about what I would expect - Didnít AMD basically market the 586-133 as a Pentium 75 equivalent?

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    Thanks for the response. Glad to know someone appreciates that. Supposedly they're supposed to be a Pentium 75 equivelent, at leats as integer performance is concerned. (They are marked P75+). I'm mildly curious how a Pentium 75 actually stacks up against a Pentium 66, as the former runs a 1.5 times a 50Mhz Bus while the latter runs at a full 66Mhz.

    Also, there is an error in that chart. Both boards were run with 32MB total, and were tested separately, with the same two sticks of 16MB ram.

  4. #4

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    That's pretty cool. If you can get your hands on one of the Cyrix 5x86 CPUs, I think you will be surprised how well they perform. I have a AMD 5x86 at 160MHz and the Cyrix 5x86 at 100MHz completely blows the doors off of it when it comes to gaming.
    Collector of socket 3, 5, 7, and 8 CPU's.
    I also love Gateway 2000 computers.

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    Quote Originally Posted by dan951 View Post
    That's pretty cool. If you can get your hands on one of the Cyrix 5x86 CPUs, I think you will be surprised how well they perform. I have a AMD 5x86 at 160MHz and the Cyrix 5x86 at 100MHz completely blows the doors off of it when it comes to gaming.
    The reason the Cyrix 5x86 beats the AMD 5x86 is because they're two different class processors. The Cyrix 5x86 is a cut down Cyrix 686MX with a 486 bus interface (much like the Intel POD63/83), while the AMD 5x86 is just a fast 486.

    The Cyrix 5x86 isn't all roses and unicorns though, it has compatibility issues. It doesn't implement the full i486 instruction set, and has very limited support of Pentium class instructions. It also would have been a much faster part if branch prediction was enabled on final silicon, which caused a bit of controversy back in the day (Cyrix advertised benchmarks with BP turned on.) There is a tool to turn it on manually, but it usually results in an unstable system.

  6. #6

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    Wasn't there also something where you ran a utility to enable the L2 cache on the 5x85 or something odd like that? I recall running something on mine back in the day that would speed it up...

    Wesley

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    Quote Originally Posted by wesleyfurr View Post
    Wasn't there also something where you ran a utility to enable the L2 cache on the 5x85 or something odd like that? I recall running something on mine back in the day that would speed it up...

    Wesley
    The Cyrix 386 FPU has a small executable to enable/disable its cache. Don't know about the Cyrix CPU.
    Surely not everyone was Kung-fu fighting

  8. #8

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    Quote Originally Posted by Agent Orange View Post
    The Cyrix 386 FPU has a small executable to enable/disable its cache. Don't know about the Cyrix CPU.
    With a little digging I found this - https://web.archive.org/web/20031020...owerBoard.html

    "Cyrix5x86
    Just put it on the ZIF socket directly and set J15 "speed" jumper unplugged. If you run
    DOS, Win3.1, Win9x or NT4, you'd better use appropriate cache programs to activate L1
    cache W/B feature.
    I've been using ET586.exe by Evergreen which is contained in et9603.exe"

    Of course that may or may not have been what I'm remembering, but that sounds right, and I do recall it helping the performance.

    Wesley

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    Quote Originally Posted by wesleyfurr View Post
    Wasn't there also something where you ran a utility to enable the L2 cache on the 5x85 or something odd like that? I recall running something on mine back in the day that would speed it up...

    Wesley
    There were several utilities that had varying capability to enable/disable 5x86 CPU features. Vogons has an extensive post covering it:

    https://www.vogons.org/viewtopic.php?t=30607

    Branch prediction has the most speedup potential, but is also the most unstable unless you have a late revision part.

  10. #10

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    Quote Originally Posted by GiGaBiTe View Post

    The Cyrix 5x86 isn't all roses and unicorns though, it has compatibility issues. It doesn't implement the full i486 instruction set, and has very limited support of Pentium class instructions.
    Considering the fact that Pentium is just a fast 486 which in turn is just a fast 386 I would strongly disagree with the above statement. Which instructions are missing??? Don't tell me about CMPXCHG or those manipulating some specific MSRs. They were avoided back in time in order to maintain software compatibility with all CPUs starting 386. The latter introduced the IA32 architecture.

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