Power Mac G4 Letters,

By Matthew Rothenberg  |  Posted 2002-09-03 Email Print this article Print

Page 4"> Power Mac G4 Letters, Page 4

There are three things that make this upgrade interesting (not looking at megahertz). They are:
1. Dual CPUs. It is true that many applications are not dual CPU-aware. However, Mac OS X is fully multiprocessor aware. The G4 architecture allows for very nice performance scaling with jobs that are inherently parallel—image processing, video editing, FFTs, Monte Carlo simulations—but lets discount all that for a minute.
At the very least, when a user is doing a computationally intensive task, one CPU takes up all the computational load, and the other CPU takes up the overhead of simply running other tasks, such as playing music, surfing internet, etc. Let us give a 25 percent performance benefit for having two CPUs. In other words, the performance megahertz is 1.25 GHz X 1.25 = 1.5625GHz (equivalent performance). 2. Mac OS X 10.2 optimization. I have not used it yet, but if you look at the info circulating on the Web, you find that 10.2 uses the graphics chips (Quartz Extreme) to do GUI jobs. These new systems ship with a very capable graphics card. In addition, if popular reports are to be believed, OS 10.2 has extensive improvements in stack management, multi-threading etc. All these improvements, with a suitable hardware should eke out at least another 10 percent performance improvement. In other words: 1.5625 X 1.1 = 1.71875GHz.
3. Architectural improvements. There are some modest architectural improvements with DDR RAM, not having a PCI bridge (as happens in PCs), and directly connecting external FireWire devices and Gigabit Ethernet cards to the bus without going through PCI traffic. This should eke out another, perhaps, 10% benefit depending on the task. (I think Apple really was hampered here because the system bus and the memory bus arent running at higher speeds—perhaps because of Motorola). In any event, the 10 percent benefit should result in 1.71875 X 1.1 = 1.9GHz. If you throw in another 15 percent floating-point performance benefit associated with the PowerPC G4 (compared to a run-of-the-mill Pentium 4), you get something close to a 1.9 X 1.15 = 2.2GHz Pentium 4 performance. If I were a power user using the best of yesterdays G4s, these upgrades represent a 80 percent to 90 percent improvement right off the bat. (These are conservative estimates.) That is nothing to sneeze at. Of course, under more ideal conditions—such as running an Altivec-optimized, multi-CPU-aware application like Photoshop), and doing a parallel-processing task (running two batch jobs simultaneously), you will be kicking some serious performance gain with a *nix OS running it. I think if Motorola really gets faster CPUs to Apple, they will be kicking the P4s butt. Moto keeps throwing lemons, and somehow Apple has been making the best lemonade (so far). Perhaps someone like you should suggest Apple start advertising these as 2.0GHz Pentium 4-performance machines! Raja Muthup

Online News Editor
Matthew has been associated with Ziff Davis' news efforts for more than a decade, including an eight-year run with the print and online versions of MacWEEK. He also helped run the news and opinion operations at ZDNet and CNet. Matthew holds a B.A. from the University of California, San Diego.


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