Greg Joswiak, vice president of hardware product marketing at Apple, has defended Apple's performance claims for its Power Mac G5, after they came under fire - reports Slashdot.

In a phone interview Joswiak insisted that they set out from the beginning to do a fair and even comparison, which is why they used an independent lab and provided full disclosure of the methods used in the tests. This would be "a silly way to do things" if Apple were intending to be deceptive, said Joswiak.

He said Veritest used gcc for both platforms, instead of Intel's compiler, simply because the benchmarks measure two things at the same time: compiler and hardware. To test the hardware alone, you must normalize the compiler out of the equation - using the same version and similar settings. If anything, Joswiak said, gcc is more optimized for Intel than for PowerPC.

Lower higher Joswiak conceded that the Dell numbers would be higher with the Intel compiler, but that the Apple numbers could be higher with a different compiler too.

He added that in the Intel modifications for the tests, Apple chose the option that provided higher scores for the Intel machine, not lower. The scores were higher under Linux than under Windows, and in the rate test, the scores were higher with hyperthreading disabled than enabled. He also said they would be happy to do the tests on Windows and with hyperthreading enabled, if people wanted it, as it would only make the G5 look better.

Of the G5 modifications, Joswiak explained that they were made because shipping systems will have those options available. For example, memory read bypass was turned on, for even though it is not on by default in the tested prototypes, it will be on by default for the shipping systems.