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Poor performance of G5 on GNOME's CPU benchmarks.

Hello everybody,

I have to admit that I have always been disappointed to the performance
of my iMac running Debian, and have a gut feeling that it is faster
under OS X. Yesterday, I found by chance a "System Profiler and
Benchmarks" facility in the GNOME Sytem menu, and ran it on my iMac and
a intel-based laptop. The benchmark provides additional references
values for a Celron M and a PowerPC 740/750, which I also have included.

The G5:
Processor	PowerPC PPC970FX, altivec supported (1800,00MHz)
Memory	745MB (204MB used)

The laptop:
Processor	2x Intel(R) Core(TM)2 CPU L7400 @ 1.50GHz
Memory	1547MB (258MB used)
(Apparently, the benchmark is not parallellised and uses only one core).


Higher is better			 Zlib	MD5	SHA1
PowerPC PPC970FX (1800,00MHz)		15701	 18	  19
Core(TM)2 CPU L7400 @ 1.50GHz		12611	 49	  56
Intel(R) Celeron(R) M 1.50GHz		 8761	 38	  49
PowerPC 740/750 (280.00MHz)		 2150	  7	   6

Lower is better			Fibonacci	Blowfish	Raytracing
PowerPC PPC970FX (1800,00MHz)          18             62                25
Core(TM)2 CPU L7400 @ 1.50GHz	        6	      21                29
Intel(R) Celeron(R) M 1.50GHz	        8	      26                40
PowerPC 740/750 (280.00MHz)	       58	     172               161

The result is that on some particular types of computations, the G5
performs extremely bad: something like twice slower as an old 1.5 Ghz
Celeron machine. For some other tests, the performances of the
processors scale with the frequency.

Is is a known characteristic of the G5, or are there specific parameters
to switch on in the kernel or whereever else to get the expected
performance of a 1.8 Ghz chip?

Have a nice day,

Charles Plessy
Tsurumi, Kanagawa, Japan

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