TOP2 probably illegal smart moves

By: Michael S (, September 29, 2009 11:04 am
Room: Moderated Discussions
Richard Cownie ( on 9/29/09 wrote:
>David Kanter ( on 9/29/09 wrote:
>>I don't think that P6 really stole much from Alpha. The really tricky part for
>>P6 was figuring out how you might get x86-->uops efficiently with sufficient ILP for OOOE.
>Yes. My impression was that it was Pentium (not PentiumPro)
>that involved more, to put it politely, disputed technology.
>The relative timing of the first Alpha AXP and the first
>Pentium would suggest that was plausible. And since Intel
>ended up paying about $700M to DEC (admittedly in a complex
>deal which bought Intel a fab and various other stuff), I
>tend to think there was some substance to DEC's claims.
>Pentium was the first time Intel went superscalar; and it
>was the first time they got in the same ballpark as RISC
>(at least the weaker RISCs - Pentium overtook SPARCstation,
>and stayed ahead as it ramped up clockspeed while
>SuperSPARC flopped). If you see a mediocre hitter who
>suddenly starts hitting 40+ home runs, you reckon he's
>probably cheating. And Intel's cpu designs made that kind
>of leap between 486 and Pentium.

The leap between 486 and Pentium had four main contributors:
1. Writeback on-chip data cache (486 on-chip cache was write through and unified with instruction cache).
2. Faster _and_ wider external bus - 4x peak throughput
3. Pipelined FPU - about 10x peak theoretical throughput over i486 and more than twice lower latency
4. 2-way superscalarity

I don't know which of the first three factors was the most important but I am pretty sure that the fourth factor (superscalarity) was not nearly as significant as either of the first three.

Do you remember what exactly, according to DEC's claim, Intel stole from them? Was it from Alpha or from VAX
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TopicPosted ByDate
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          the generic mechanismAM2009/09/27 01:15 AM
            the generic mechanism?2009/09/27 02:30 AM
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            TOP3 blunders?2009/09/27 08:33 AM
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              TOP3 blundersslacker2009/09/29 07:28 AM
                (12nJ/cycle)*3GHz = 36W (NT)Michael S2009/09/29 08:31 AM
                  That's what I get for posting so early. (NT)slacker2009/09/29 06:17 PM
          TOP3 blunderskoby m.2009/09/29 07:26 AM
            TOP3 blundersJouni Osmala2009/09/29 11:05 PM
              TOP3 blunders?2009/09/30 02:26 AM
    TOP3 blundersPotatoswatter2009/09/26 07:11 AM
      TOP3 blunderssomeone2009/09/26 09:26 AM
    ISA extensions - tensilica?David Kanter2009/09/26 10:17 AM
      ISA extensions - StretchWes Felter2009/09/26 11:24 AM
        ISA extensions - Stretch?2009/09/26 01:14 PM
          ISA extensions - StretchGabriele Svelto2009/09/28 03:14 AM
  TOP3 blundersanonymous2009/09/26 06:23 AM
  TOP3 smart movesanonib2009/09/26 07:11 PM
    TOP3 smart movesDavid W. Hess2009/09/26 07:55 PM
      TOP3 smart movesRichard Cownie2009/09/27 01:57 PM
        TOP3 smart movesRagingDragon2009/09/28 03:46 PM
    TOP3 smart movesa reader2009/09/27 08:44 AM
    TOP3 smart movesRichard Cownie2009/09/27 12:12 PM
      TOP2 probably illegal smart movesRichard Cownie2009/09/27 01:43 PM
        TOP2 probably illegal smart movesnn2009/09/27 07:27 PM
        TOP2 probably illegal smart movesDavid Kanter2009/09/29 01:48 AM
          TOP2 probably illegal smart movesRichard Cownie2009/09/29 10:31 AM
            TOP2 probably illegal smart movesMichael S2009/09/29 11:04 AM
              TOP2 probably illegal smart movesDavid Kanter2009/09/29 01:35 PM
              TOP2 probably illegal smart movesRichard Cownie2009/09/29 04:28 PM
              TOP2 probably illegal smart movesJouni Osmala2009/09/29 11:08 PM
              Link to good analysis on the matter.Jouni Osmala2009/09/29 11:22 PM
                Link to good analysis on the matter.Richard Cownie2009/09/30 09:59 AM
  TOP3 blunder of todayMichael S2009/09/29 04:31 AM
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