By now most have heard Apple's mantra. Megahertz are a myth. Or something like that. If you believe Apple's corporate propaganda, you might believe that Intel's megahertz are second-class citizens when compared with Motorola's. Depending on which flavor of Kool-Aid you're drinking, various Apple PR related materials suggest that it takes two-or-three Intel Pentium cycles under Windows to equate to a single Motorola G4 cycle under OS X. Don't believe the hype. In practice, if anything, the converse seems more likely to be true. If you want Apple's OS X to perform common functions at around the same speed as an Intel Pentium III (P3) system running Windows XP, you will need roughly two G4 cycles for every one P3 cycle.

The Tests
What do I base this on? Some tremendously unscientific tests, and some empirical and anecdotal evidence as well. Now, no one is arguing that a G4 is more efficient per clock cycle than a P3/P4 in a vacuum; however, we don't live and work in a vacuum. The real world demands functionality throughput, not processor throughput. How fast can you perform certain functionality, like scrolling, or loading a Web page? And in the real world, OS X and its applications exact a performance tax causing Macs to run more slowly. As such, Macintosh G4s cannot deliver two-or-three times greater throughput for average functionality. Perhaps the G4 is 30-40% more efficient in a vacuum, which is great, but the disparity in overall available hertz is well over 100% in Intel's favor (i.e., 1.42 Ghz G4 vs. 3.06 Ghz P4), which compounds the performance gap between Macs and PC systems. With those provisos out of the way, here are my unscientific test reference systems:

I chose a bunch of programs in an attempt to mimic common operations for users, and ran a battery of tests, which were timed by stopwatch. I ran the following tests (three times, taking the average) on both systems using the exact same documents. I didn’t include the standard Photoshop tests because (1) the average person isn’t using Photoshop in any heavy way, and (2) everyone seems to concoct Photoshop tests that rely so heavily on processor media acceleration functions, whether AltiVec, or MMX/SIMD/iSSE, that the results only suggest that optimizing application code for media acceleration is more important than any design differences between processors.

Instead, I did scrolling tests because that is one of the most common user/computer interactions—a user might regularly scroll hundreds of times a day. Another frequent user activity that served as a test was loading and rendering a Web page. All documents and Web pages were opened to roughly the same visible window dimensions on each system. I used this Slashdot.com thread for a test Web page. I used a 194 page patent application with moderate formatting and no graphics for a test Word document. I also ran a Word macro to renumber the patent claims in the Word document; the macro comprises relatively intense find/replace, copy/paste and recalculation functionality. A 72 page "AGFA SnapScan[ner] 600 User's Manual," filled with art, was used for the PDF test document. I then re-ran these tests under a heavy load, which included running LimeWire, QuickTime looping through the new Matrix trailer, and iTunes looping "Breathe" by télépopmusik, all in the background. I also tested the boot-up time for each system from power-on until my login applications were completely loaded. Finally, I measured delays in switching between applications' windows and drawing selected menus.

The Results
Here are the unexpected tests results, which are all measured in seconds or percentage use of the CPU:

Basically, the P3 system spanked the G4. On the PC, scrolling and navigating through Word is instantaneous; scrolling redraw on the PC appears to move text lightly into view as if it were etched on a slab of granite. Conversely, the Mac's display/redraw feels, relatively, like you're manipulating it through molasses when you try live scrolling, particularly under heavy loads. Aqua is an appropriate moniker in this regard; when I grab the scroller and drag it, the screen updates in waves and splashes. I observed a similar performance differential when resizing windows; however, Aqua uses a far better redraw technique, which does not cause redraw "blitter" evident in Windows.

Worse yet, OS X multitasking is more painful. If I play iTunes, run LimeWire, run QuickTime, and run Word on the Mac, the system becomes unresponsive. It's like I'm trying to perform brain surgery with mops tied to my hands. To Apple's credit, even under heavy load, OS X never dropped QuickTime audio, while QuickTime audio dropout was severe under Windows XP. Under heavy load, video frame dropout of the QuickTime movie was severe for both systems. Otherwise, Windows XP was much more responsive under load in almost every other way. In particular, user interactions (i.e., moving windows, scrolling text, engaging menu selections, etc.) were much more responsive on the XP system when multitasking. More impressive still, XP did so running a slew of additional applications (including the ATI TV, which never dropped a frame of video or audio, and Norton System Works, which is a performance hog). Impressively, both systems experienced no MP3 audio dropout.

Of course, the above tests are not scientific, but they are symptomatic -- indicative rather than definitive. I can't imagine what a 3.06 Ghz P4 would do to a 1.42 Ghz G4. As it stands, I was surprised that my lowly 500 Mhz P3 system so soundly trounced all over my 667 Mhz G4 -- leaving my PowerBook's keyboard-marred screen and chipped-titanium carcass in its wake.

Reality Disparity
So why the apparent disparity between the PR claims and reality? Well, the truth is that overall system throughput is more complicated to measure and varies based on things other than just processor pipeline length or raw megahertz. It also depends greatly on operating system efficiency, efficiency in handling spin locks and context switches, shared runtime library efficiency, program code efficiency, compiler optimizations, memory bandwidth, instruction set capabilities and efficiency, etc. Sure the AltiVec processing units on the G4 do a great job of accelerating vector processing functions, but how about the more mundane activities that are executed far more often?

Lets not forget, OS X is an operating system that requires more horsepower to provide much of its advanced functionality; it's simply doing more stuff. For example, a pervasive object layer, which provides huge libraries of functionality (e.g., where any text box can be spell checked), takes its toll. Also, providing real-time display-PDF, which is animated and composited in 3D alpha-transparency layers, to your screen taxes the system. Such robust, extreme and beautiful technology and OS X's greater capabilities compound the need for speed on the platform. Apple's system is often, and I believe rightfully, considered to be the most advanced and vital operating system available for general computing applications. Nevertheless, from the end user's perspective, the result is painful. You need two hertz from a Motorola G4 under OS X to get similar performance to a single hertz from an Intel Pentium III under Windows XP. In other words, a 1 Ghz G4 is almost a requirement for a decent experience with OS X.

Reality Distortion Expected
I cannot blame Apple for trying to spin its lemons into lemonade. I expect it. They have been dealt a bad hand from Motorola as of late. So it stands to reason that its megahertz myth video talks of pipe-line efficiency, yet Apple subtly switches to discussions of AltiVec acceleration on its Web page to tout a two-to-three time speed boost, which has a lot less to do with the over-explained pipeline differential, and more to do with far less used vector functionality. No matter how snazzy John Rubenstein's Keynote presentations are, megahertz does matter. Sure, not all megahertz are created equal, but overall system throughput and disparities can at least, roughly, be measured and compared.

However, many seem to be in some kind of denial about the woeful state of performance of OS X on G4s. In that regard, the press has been slacking. I'm not sure if they've all gone to the Apple Kool-Aid trough one too many times, or if there are other externalities at play. It seems strange to me that such performance disparity and the high prices of Apple's offerings are not more of an issue to the press. Supposedly it is their job to question and bring such issues to everyone's attention, but instead, everything is sugarcoated. It's as if Mac pundits have their heads so far up Apple's ass that they can't see things for what they are. Current Macintosh systems are slow compared to current Microsoft XP systems. Apple needs to provide significantly faster machines, and they cannot come soon enough.

Then again, maybe it's just me. As always, your mileage (and perception of speed) may vary.