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Skidmarks GT

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Year released:
[www].se [ftp].se [mirror].us (461.91 KB)
MD5: 6e017c93472074ca51a577c212dfb6f7
For Mac OS X
Guides on emulating older applications

Apple made this little CPU benchmark utility and included it in the Developer Tools for OS X PPC. It was removed from the tools during the Intel CPU switchover even though new releases of OS X continued to support PowerPC for four more years.

The motif is auto racing tied to CPU performance: Skidmarks is burning rubber, GT means Gran Turismo, the icon is a checkered finish line flag - you get the idea.

It makes a nifty profiler to see whether the G4's AltiVec unit is enabled or disabled. Run the small test and if AltiVec hardware is off or absent, then the "Vec" result box is blank. Functioning AltiVec provides a Vec number.

Results are typically one tenth the CPU speed, hence the 158 in the screenshot is from my 1583 MHz G4 7455B. When CPU caches are disabled, the score will fall drastically and may become super sensitive to other hardware like RAM and video DMA. There are detailed subtest results if requested, seen in the 2nd screenshot here and the column headings labeled "(us)" must be a shorthand abbreviation for "micro seconds". It is neato how the last column is in percentage units meaning the 158 score of my 1583 MHz CPU is the average percentage (158% better than 1.0 GHz) in a set of several tests.

Architecture: PPC

For PowerPC and its CPUs.
Download contains 2 versions: 3.0.0 from 2003 (Panther) and 4.0.1 from 2005 (Tiger).
Runs in Jaguar and Leopard too.


Jatoba's picture
by Jatoba - 2020, April 17 - 8:10am

@SkyCapt Huh... I guess it does make sense that if there is overreliance on AltiVec (or any other processing unit) and it is then misused or not used adequately, you may benefit by missing out on a feature or two but gain speed by disabling it. Or even if it is used adequately, if its presence is associated with extra features being present, and they slow things down, and you'd rather turn the features off, but the software doesn't allow you to conveniently turn it off, you gain speed by disabling the processing module behind it itself (which works as long as the program checks for its presence first and, if not present, has a fallback option, of course).

Interesting use case for disabled AltiVec. It reminds me of the extra importance of coding things well. We ought not to get carried away by overabundance of RAM, GPU, general processing power etc. in today's computers if we want to do a job really well-done (good design first, good resources later). Likewise, if the software "gets carried away" by the presence of AltiVec, its AltiVec features should at least be able of being toggled on and off, so that the user wouldn't have to try toggling on and off AltiVec itself.

SkyCapt's picture
by SkyCapt - 2020, April 16 - 11:42pm

FPU could be found "turned off" when the computer is inside the firmware mode during its initial boot. Altivec shutting off is very fun to play with. For a while I ran it permanently off because OSX 10.4.11 or QT > around 7.3 was slower than OSX 10.4.8 and no Altivec stopped that and made 10.4.11 faster than 10.4.8 if I recall. Then, after changing my machine id from G4 to G5 I no longer got slowed down by Tiger updates so I could use 10.4.11 with Altivec enabled. Then when I first learned how to disable Beam Sync in 10.4.11 but not in 10.4.8 - 10.4.11 became faster than 10.4.8 - but I quickly learned how also to disable Beam Sync in 10.4.8 so still nothing beats 10.4.8

With a fast CPU like 1.5 GHz, little difference and no harm comes from disabling Altivec. But we can hunt down some things. Music encoded by iTunes will not include vector decoding maps. They actually play back more efficiently this way on my system, because my audio coprocessor can handle the job 100% whereas if AAC music files are with vector decoding then it requires CPU activity to play back the music. Ironic. The best thing (still, to this day) is DVD Player. I have to hack their stupid software, but when I do, and Altivec is disabled, my Tiger Apple DVD Player gets more than twice as fast so that "slow motion" plays faster than real life 1x, faster than 40 fps, and there's no "residual deinterlacing effects" splattered around any more.


Minus 55 thousand percent... Ya, skidmarks is trying to locate hardware you don't have. That's why I categorized this page as both a dev tool and "hardware support" in which @Daxeria just removed the classification of "hardware support".

24bit's picture
by 24bit - 2020, April 16 - 7:38pm

Thanks for this one.
How do you read Quicksort minus 55 thousand percent? Smile
(VMWare 10, Leopard Server on Mojave i5-2520m)

Test Name Base (us) Test (us) Test (%)
ParseVid (INT) 148.8 46.2 321.9%
MPEG (INT) 135.1 43.9 307.8%
PixBlend (INT) 188.3 75.7 248.6%
Ellipticrypt (INT) 109.1 53.6 203.7%
Rijndael (INT) 141.3 -0.5 -30733.7%
Quicksort (INT) 253.4 -0.5 -55116.2%
MDCT (FP) 154.9 -0.4 -39947.8%
IntToFloat (FP) 88.2 25.6 344.2%
Q3 (FP) 114.4 -0.5 -24882.8%
FFT (FP) 71.7 -0.5 -15595.2%
VolInt (FP) 129.9 -0.5 -28254.1%
Quant (VMX) 96.5 43.2 223.4%
Galaxy (VMX) 127.6 55.7 229.2%
IDCT (VMX) 91.9 -0.5 -19988.9%
BigMult (VMX) 167.0 15.7 1066.7%

Skidmarks completed successfully!

Jatoba's picture
by Jatoba - 2020, April 16 - 4:37pm

I like this. I didn't know (or I forgot) AltiVec could be turned off. Yikes. I wonder why anyone would do that? Less electricity drain? Nonetheless, I appreciate learning of the existence of this being a possibility. But what's next? Can we turn off the FPU, too? Tongue