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|Architosh News Reports|
|Architosh Staff ([email protected])|
G4 vs Pentium and AMD Athlon performance data
With the announcement of the G4 processor, a 'supercomputer' on a chip, Intel and other industry experts challenged Apple's claims, which were based on Intel's own tests and specifications. Moreover, recently Intel has been taking a media hit with the AMD Athlon processors beating out Intel's latest and greatest chips. Now the G4 ads will rub it in even further with Apple's new Tank commercial -- a TV ad which features the G4's 'supercomputer' status, being the subject of US government protection and export control. But how fast exactly is the G4 over the Pentium III in the industry standard SPECfp95 (floating-point) tests?
The following chart of scores makes one fact very clear: Whereas the G3 made a large leap in integer performance, the G4 makes a quantum advancement in floating-point performance -- thus the gigaflop 'supercomputer' status. A "flop" stands for floating-point operations per second, and the G4 can sustain a billion of them with theoretical limits of 4 gigaflops.
Floating-point Performance Enhancements over G3
Motorola's website data only list estimated values of SPEC95 scores for the 450 MHz version of the PowerPC7400 (G4). Looking at percentage differentials for the G3's one can make a safe estimate that the 400 MHz G4 processor has an SPECfp95 score around 90 percent that of the 450 MHz version which puts it around 18.36. [Editor's correction] That is a 50% improvement in floating-point scores over the G3 at the same clock rate. Please note that 90% differentials on the G3 line don't necessarily imply the same for the G4's.
According to information published last week in a Macworld article, the G4's floating-point unit (FPU) -- which is used extensively in 3D rendering/modeling, animation, video, special effect filters and scientific applications -- alone is up to 25% faster in the G4. That means that without a program's use of the vector unit (Velocity Engine) unaltered existing applications will noticeably improve in floating-point performance. [Editors correction] At the same clock rate, such applications when compared to their speed on G3's will run at least 50% faster (1.5x) on up to 10x or even 15x faster when the program takes advantage of the AltiVec instruction set (Velocity Engine).
The bottom line is, if floating-point apps are your game you can't live without a G4. The performance gains, especially when running AltiVec-enabled apps, will be tremendous over the G3.
Floating-point performance compared to the Pentium III and AMD Athlon
Compared to rival Wintel processors by Intel and AMD, the G4 smokes them all (even at much lower clock speeds), except for the new AMD Athlon chip. The Athlon chip has impressive scores for both floating-point and integer performance. The following SPECfp95 scores were taken from Intel's and AMD's website, and on the Pentiums are based on Windows NT 4.0 systems. Windows 95/98 scores would most likely be lower. Also of note, the AMD Athlon scores are based on a motherboard that is not yet shipping, according to the AMD website.
Some closing thoughts about the floating-point performance numbers. When the G3 came out its floating-point numbers were very close to the then rival Pentium II. Where the G3 smoked the Pentium II was at integer performance. For instance, the 300 MHz G3 had a SPECint95 score of 14.2 compared to a 300 MHz Pentium III SPECint95 score of 11.9. However, those two chips had 10.3 and 8.1 SPECfp95 scores, respectively -- much tighter competition on this test suite.
Now the G4 has taken a huge jump forward on the floating-point performance as measured by the SPECfp95 test suite. Even the G4 400 MHz chip has a larger differential over the Pentium III 600 MHz then the rival of G3 over Pentium II at the same clock speed. Just think! What would the differential be for a 600 MHz G4? Using the same method of calculating 50 MHz advances in the G4 line ( a given chip produces a SPECfp95 score that is 90% of a chip 50 MHz faster) a G4 at 600 MHz would produce an estimated SPECfp95 score around 27.9 compared to the 15.9 SPECfp95 score of the 600 MHz Pentium III.
The G4 and Macintosh CAD and 3D Applications
For those who made the transition to G3 processors from either lower clock cycle 604e's or 601 or 603 PowerPC's, the biggest sense of speed up was probably in the OS itself, with the Finder and other parts of the Mac operating system finely tuned and optimized for the G3. Mac OS 8.5 further sped up the Finder with a PowerPC-native QuickDraw engine tuned for the G3.
This windowing speed up is important for CAD users. CAD users jump in and out of views, move palettes around a lot and jump in and out of other applications while working in general. The G3 did a lot for that. However, floating-point performance improvements with the G3 may have been less noticeable, depending on your situation. The G4 is about to change all of that for all users, including G3 users. The G4 is significantly faster at floating-point calculations!
John Carmack, of iD Software, the legendary game programmer who Jobs brought on stage at Macworld Expo San Francisco last January, made comments recently about the initial G4 400 MHz systems. He noted that there will be some speed up in normal C code from the faster FPU (again about 25% faster at the same clock rate). In addition, the Apple OpenGL implementation has AltiVec optimizations. This will benefit everybody using an OpenGL application, regardless of whether the rest of the app has been optimized for the vector unit or not. John also noted that after Apple tunes their drivers for the new G4 they may have the best non-geometry acceleration throughput out there, with the exception (perhaps) of the new Athlon chips.
So if you've been waiting to get a new system for CAD and 3D work, and are currently in doubt about whether to skip the 400 MHz G4 on the old motherboard or wait for the 450 MHz G4 on the new Sawtooth motherboard, don't be in doubt too much. The initial system has much to offer in the way of speed improvements. This is especially true if you do a lot of 3D rendering work or use other applications that are floating-point intensive. And if you applications use OpenGL you will benefit there as well due to the AltiVec optimizations. For roughly $900 less then the low-end Sawtooth machine, the 400 MHz G4 model -- shipping right now -- kicks serious butt on the Pentium III and the fastest old G3's.
Editor's Note: Thanks to all those readers who pointed out the percentage calculation mistake. The floating-point SPECfp_95 scores for the G4 make a 50% improvement over the same scores for the G3 at the same clock speed.
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