POWER7 Spec

By: Michael S (already5chosen.delete@this.yahoo.com), February 9, 2010 9:08 am
Room: Moderated Discussions
Ian Ameline (ian.ameline@gmail.omitthis.com) on 2/9/10 wrote:
---------------------------
>Thu Nguyen (thunng8@hotmail.com) on 2/8/10 wrote:
>---------------------------
>>Ian Ameline (ian.ameline@gmail.com) on 2/8/10 wrote:
>>---------------------------
>>
>
>Very true. It is interesting, however, that with an L1$ that is twice as fast,
>double the register file size, double the L3 cache size, and double the FP execution
>resources, that they don't do even better than this.
>
>-- Ian.

"Double the FP execution resources" is a somewhat misleading.
In certain circumstances (LINPACK and the likes) dual FMAC of POWER7 is indeed "double" relatively to Nehalem's separate FADD+FMUL, however that's far from universal. On average.
a) FADD is more common than FMUL
b) Not all FMULs can be fused into FMACs

Took, for example, Radix2 FFT butterfly. Given infinite unrolling on FADD+FMUL hardware it could be executed at 6 clocks/iteration. On dual-FMAC you still need no less than 4 clocks/iteration. IMHO, the ratio of 1.5 as in Radix2 butterfly is more typical than ratio of 2 seen in the LINPACK/DGEMM.
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TopicPosted ByDate
POWER7 SpecParadox2010/02/08 11:05 AM
  POWER7 SpecThu Nguyen2010/02/08 12:58 PM
    POWER7 SpecIan Ameline2010/02/08 09:22 PM
      POWER7 SpecThu Nguyen2010/02/08 11:54 PM
        POWER7 SpecIan Ameline2010/02/09 06:46 AM
          POWER7 SpecLinus Torvalds2010/02/09 07:57 AM
            industry-standard single-threaded performance benchmarks absentMichael S2010/02/09 08:09 AM
              industry-standard single-threaded performance benchmarks absentParadox2010/02/09 08:33 AM
                industry-standard single-threaded performance benchmarks absentMichael S2010/02/09 09:30 AM
                  industry-standard single-threaded performance benchmarks absentParadox2010/02/09 10:52 AM
                    industry-standard single-threaded performance benchmarks absentJesper Frimann2010/02/09 11:33 AM
              industry-standard single-threaded performance benchmarks absentLinus Torvalds2010/02/09 08:48 AM
                industry-standard single-threaded performance benchmarks absentMichael S2010/02/09 09:26 AM
                  industry-standard single-threaded performance benchmarks absentLinus Torvalds2010/02/09 09:58 AM
                    industry-standard single-threaded performance benchmarks absentJesper Frimann2010/02/09 12:17 PM
                      industry-standard single-threaded performance benchmarks absentLinus Torvalds2010/02/09 12:54 PM
                        industry-standard single-threaded performance benchmarks absentJesper Frimann2010/02/09 02:10 PM
                    industry-standard single-threaded performance benchmarks absentParadox2010/02/09 01:22 PM
                industry-standard single-threaded performance benchmarks absentanon2010/02/09 10:21 AM
            POWER7 SpecJesper Frimann2010/02/09 12:30 PM
            POWER7 SpecDoug Siebert2010/02/09 05:38 PM
              POWER7 SpecLinus Torvalds2010/02/09 07:28 PM
                POWER7 SpecLinus Torvalds2010/02/09 07:28 PM
                  POWER7 SpecIan Ameline2010/02/09 08:02 PM
                    POWER7 SpecDoug Siebert2010/02/09 10:18 PM
                POWER7 Specsomeone2010/02/09 08:20 PM
                  POWER7 SpecLinus Torvalds2010/02/10 09:17 AM
                    POWER7 SpecLinus Torvalds2010/02/10 09:46 AM
                      POWER7 SpecEmil2010/02/10 11:06 AM
                    POWER7 SpecIan Ameline2010/02/10 10:13 AM
                    POWER7 Specsomeone2010/02/10 11:01 AM
                      POWER7 SpecLinus Torvalds2010/02/10 11:32 AM
                        POWER7 SpecMichael S2010/02/10 12:30 PM
                          POWER7 SpecLinus Torvalds2010/02/10 01:25 PM
                            POWER7 Specmpx2010/02/10 02:58 PM
                        POWER7 Specnemlis2010/02/11 12:24 AM
                          POWER7 Specnone2010/02/11 12:52 AM
                            POWER7 Specnemlis2010/02/11 01:52 PM
          POWER7 Specmpx2010/02/09 08:18 AM
          POWER7 SpecMichael S2010/02/09 09:08 AM
        POWER7 SpecJesper Frimann2010/02/16 02:29 AM
          POWER7 SpecJamie Lucier2010/02/16 06:35 AM
            POWER7 Specanon2010/02/16 07:16 AM
              POWER7 SpecJamie Lucier2010/02/16 10:46 AM
                POWER7 Specanon2010/02/16 03:42 PM
                  POWER7 SpecJamie Lucier2010/02/18 06:07 AM
              POWER7 SpecThu Nguyen2010/02/16 01:23 PM
            POWER7 SpecParadox2010/02/16 09:57 AM
              POWER7 SpecJamie Lucier2010/02/16 11:22 AM
                POWER7 SpecParadox2010/02/16 02:00 PM
            POWER7 SpecJesper Frimann2010/02/16 02:14 PM
              POWER7 SpecJamie Lucier2010/02/17 10:41 AM
  POWER7 SpecJesper Frimann2010/02/09 04:43 AM
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