POWER5 is out, and it's FAST

IBM today officially announced the eServer p5, which uses their POWER5 CPU.

Why should Mac users care? Well, the G5 is based off the POWER4 series, and it's widely expected that the next-gen CPUs Apple will use will be based off the POWER5. And judging by the POWER5 benchmarks (PDF), POWER5 is extremely fast:

SPECfp2000
POWER4+ @ 1.7 GHz - 1642
POWER5 @ 1.9 GHz - 2576

Despite only a 12% increase in clock speed, there is a 57% increase in performance for the POWER5. Clock for clock, POWER5 is 40% faster than POWER4+. Not to mention it bests the fastest Itanium 2 (2161) Intel has to offer, by nearly 20%. Very impressive.

Some improvements the POWER5 brings:

SMT: Presumably one of the big factors in the speedup is the addition of simultaneous multithreading. I suspect that a POWER5 derivative (G6?) will retain this feature, at least for chips in high end desktops (aka Power Macs). In a nutshell, SMT allows the CPU to be seen as if it were dual processors. (For those of you used to PC hardware, it's called Hyperthreading by Intel.) If POWER5-lite does indeed have SMT, a dual Power Mac would be seen by OS X (10.4 Tiger?) as quad processors. It wouldn't be as fast as a true quad Power Mac of course, but the potential speed boost would still be substantial for certain (multi-threaded) apps.

IMC: Another benefit of the POWER5 design is an integrated memory controller. (Think AMD Opteron for you PC types.) This could also be included in POWER5-lite, potentially increasing memory bandwidth in future dual Power Macs. An integrated memory controller could also potentially decrease overall power usage for POWER5-derived chips in PowerBooks in the (distant) future.

L2: The POWER5 has a larger L2 cache than POWER4+. It's likely a G6 would also sport a larger L2 cache than 512 KB in the G5.

I do find it curious that IBM does not publish SPECint2000 scores for the POWER5 however. Is it because the integer scores are merely mediocre? If so, will that mediocrity in integer performance be reflected in the POWER5-lite too?

So when will we see the POWER5-lite anyway? Well, who knows... Steve Jobs last year stated he expected 3 GHz by now, but we don't know if that 3 GHz was going to be another G5 or something else. I'd guess that the 3 GHz will still be a G5 (970FX), possibly announced at Macworld January 2005, with the G6 not coming out until much later in 2005.

BTW, OS X 10.4 Tiger will include GCC 3.5 in Xcode 2.0, with support for autovectorization. IBM's uber-fast XL compilers will also be updated, including support for autovectorization, by the time Tiger is out. We won't all have to buy new G5s (or G6s) to get faster performance. :)