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Thread: AMD 486 dx4 100Mhz thoughts

  1. #1

    Default AMD 486 dx4 100Mhz thoughts

    Following my reddit post on my "new" AMD 486 dx4-100 that ended up getting lots of reactions, I decided to do a video on this computer.

    I want to go over its gorgeous mini tower case, the components and the AMD DX4 100Mhz cpu on my youtube channel

    I've done some research on the AMD DX4-100, but never owned one myself back in the day. I was wondering if anybody here had some thoughts / anekdotes or other cool facts / figures on this CPU.

    What I'm currently thinking of covering :

    • Very fast 486 cpu, perhaps a bit slower than intel 486 dx4 100 depending on the L1 cache size, but a lot cheaper
    • Came in a time period were the shift to pentium based PCs was very much ongoing
    • 8kb internal cache vs the 16kb cache in the intel based cpu, later revisions featured 16kb cache
    • 3v cpu, so don't put it in a 5v based system
    • Originally released in 1994, but revised in 1995 following an intel lawsuit. (ICE microcode)
    • Could compete to some degree with the early pentiums
    • AMD's DX4-100 being cheaper than Intel's DX2-66 (49$ vs 59$ in sep 1996)
    • ICE lawsuit with intel
    • earlier (700 nm) models operating at 5V, around late 1994/95 entered 500nm and introduced 3.3V models
    • different cache options at a later stage (write back / 16kb L1 cache)
    • Windows logo on the die to highlight the windows compatibility over general x86 compatability.


    Thanks a lot....

  2. #2

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    Quote Originally Posted by RetroSpector78 View Post
    [*]Could compete to some degree with the early pentiums
    Hardly...
    Am5x86 @ 133 MHz was supposed to be equivalent to Pentium 75, in fixed-point instructions.
    So, DX4-100 can probably compete with Pentium 60, but again - only in fixed-point, it's sure to be slower in floating-point.
    Poor floating-point performance became painful when MP3s appeared...

    BTW: I'm wondering why DX4 is called DX4, and not DX3 - after all, its core/FSB frequency ratio is 3.

  3. #3

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    Quote Originally Posted by Xacalite View Post
    BTW: I'm wondering why DX4 is called DX4, and not DX3 - after all, its core/FSB frequency ratio is 3.
    There was a legal issue over trademarks with AMD that caused that naming scheme.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  4. #4

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    Please back up the claim that there was a 5V .7 micron DX4 from AMD. I have never seen or heard of such a thing. I suspect if it exists, it's only an ES. I know for a fact that the latest models were .35 micron. Intel used .6 micron for their own DX4, so you're possibly right that AMD's earlier version was .7 micron, but I am pretty sure it was still 3.3v.
    "Will the Highways on the internets become more few?"

    V'Ger XT

  5. #5

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    Is that the original AMD 486DX4 or the Enhanced 486DX4?

    The original AMD 486DX4 had 8 kB of write-through cache, versus the 16 kB write-through cache in Intel's original 486DX4.

    AMD then introduced the Enhanced 486DX4 with 8 kB of write-back cache, which was faster. Intel responded by changing their 16 kB cache to write-back as well, on their DX4 chips made beginning in October 1994 marked as "&EW".

    AMD then played catch-up by increasing the Enhanced 486DX4's cache to 16 kB to match. (By then it was really just an Am5x86 chip without the 4X multiplier.)

  6. #6

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    I think I heard a rumour that the AMD DX4s with 16kb were really just rebadged DX5s. As far as I know, they're all 4X multiplier capable. In any case, these didn't show up until the 486 was horribly obsolete.
    "Will the Highways on the internets become more few?"

    V'Ger XT

  7. #7

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    According to info on Vogons, the AMD Enhanced 486DX4 with 16 kB write-back cache (code SV16B) came out a year after the AMD 5x86. It seems very rare.

    And then there's the OEM-only 90 MHz version of the AMD 486DX4:

    http://www.x86-guide.com/en/cpu/AMD-...cpu-no871.html


  8. #8

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    Quote Originally Posted by Anonymous Coward View Post
    Please back up the claim that there was a 5V .7 micron DX4 from AMD. I have never seen or heard of such a thing. I suspect if it exists, it's only an ES. I know for a fact that the latest models were .35 micron. Intel used .6 micron for their own DX4, so you're possibly right that AMD's earlier version was .7 micron, but I am pretty sure it was still 3.3v.
    I read on https://en.wikichip.org/wiki/amd/am486 that "Earliest (700 nm) models operated at 5V, when AMD undergone a process shrink around late 1994/95 they introduced 3.3V models.", but I guess they are referring to the am486 in general and not the DX4 in particular. Thx for pointing that out.

  9. #9

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    Quote Originally Posted by RetroSpector78 View Post
    I read on https://en.wikichip.org/wiki/amd/am486 that "Earliest (700 nm) models operated at 5V, when AMD undergone a process shrink around late 1994/95 they introduced 3.3V models.", but I guess they are referring to the am486 in general and not the DX4 in particular. Thx for pointing that out.
    According to that wikichip, the non-enhanced versions of DX4 should be .5 micron, which sounds about right to me. However, I don't know how much faith I'd put into the wikichip, because it lists this: "Am486DX2-100V16B"
    I am pretty sure there were not DX2-100s, and the only place I can find that references it is wikichip.

    The DX4-90s were a real thing though. I even remember seeing a lot for sale in the paper, thinking it was some sort of typo. I *think* these chips were mainly produced for a special Compaq model, but I also know they sold them barebones on special 486 boards that could do a 30MHz bus.
    "Will the Highways on the internets become more few?"

    V'Ger XT

  10. #10
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    I think I seen that funky 90mhz 486 in a bin at a recyclers ages ago but I passed it up for some 133 overdrives that were actually useful (built in fan and jumpers for settings). I did pick up some socketed 486/sx chips plus some other goodies.
    What I collect: 68K/Early PPC Mac, DOS/Win 3.1 era machines, Amiga/ST, C64/128
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