Is the G3 PowerPC 'twice as fast'-- Well, maybe

by Alan Zisman (c) 1998. First published in Canadian Computer Wholesaler, August 1998

You?ve probably seen the ads on TV?perhaps the series with the snails ?racing? along with Intel Pentium-II processors strapped to their backs. Or others from Apple Corporation, all ending with the same claim?that the G3 PowerPC CPU in Apple?s Macintosh computers is up to twice as powerful as comparable-speed Pentium-IIs.

At the Spring launch of Apple?s G3 Powerbook notebooks and iMac home computer, Apple more-or-less chairman Steve Jobs made the same boast, and showed off a couple of demonstrations aimed at proving the point. He let a 266 MHz G3 machine go up against both 266 and 400 MHz P-II hardware, running first a complex Adobe Photoshop macro, then running a Macromedia Director animation.

In each case, the Macintosh handily outpaced even the 400 MHz P-II computer, lending credence to Jobs? claims that a G3 PowerPC is the equivalent of a Pentium-II running at twice the clock speed.

But is a G3-powered machine actually ?up to twice as powerful??

There?s no doubt about it?from the beginning, the PowerPC, originally designed by IBM, and built by Motorola, is a powerful CPU. It uses a RISC design that is in many ways more efficient than the 80x86 design that Intel has steadily evolved since the 1970s. And the G3 (for Third Generation) PPC was the first series designed specifically for Apple hardware. At the same time, Apple?s operating system has steadily become more ?PowerPC Native?. The result is a processor and operating system that are, to a large extent, designed for each other.

Using advanced 0.25 micron fabrication, and drawing only 5 watts power, the G3 runs cool enough that it doesn?t need a fan. It features 64 kb of L1 cache, built into the CPU, and 1 meg of L2 cache?in both cases, twice the amount of a Pentium-II. G3 motherboards run at 83 MHz, faster than the 66 MHz of all but the latest generation of P-IIs (and faster than any current PC laptops).

The result is a hardware design that, as suggested in the Apple ads and demos, screams?at least in some applications. Much depends, however, on the application chosen for the demonstration, and in some cases, on the specific functions chosen within the same application.

And that?s what makes it hard to make comparisons that hold up in real life. Apple made much of benchmarking carried out by Byte Magazine?trying to focus in on the CPUs, the Bytemark integer processor tests suggested that indeed, a 200 MHz PPC and a 400 MHz P-II scored in the same range. Hence the Apple ads.

But CPUs are only one part of a computer system. In real computers, performance depends on CPU power (score one for Apple), but also on the amount of cache (score another for Apple), and on system bus speed (either Apple or Intel scores, depending on model used). And on hard drive and video performance. And on operating system (minority operating systems like Linux or the BeOS can provide some pretty impressive demos on otherwise run-of-the-mill hardware). And on the software used. Microsoft Office 4.2, for n example, was well known as an inefficient slowpoke on the Mac, while its replacement, Office 98, includes ?quick loading code? that is a generation in advance of Office 97 for PCs.

So when comparing actual applications on actual computer systems, it?s not always easy to know how to interpret results.

Here are the results of some real-world tests:

  • PC Magazine compared a 250 MHz Apple G3 notebook with a 300 MHz P-II desktop. They tested a number of functions in Adobe Photoshop 4.0.1: Resize, Gaussian Blur, Unsharpen Mask, Lighting Effects, and Rotate, on a 10 meg TIF graphic. They spent some time, optimizing memory settings on the Mac (Windows 95 handles that automatically). Their results: ?The G3 was slightly faster than the PC on Resize and Lighting Effects but marginally slower on Gaussian Blur, Unsharpen Mask, and Rotate.?
 But when they used Word and Excel as the basis for their tests, the G3 took, on average, almost twice as long.
  • Some might respond that PC Magazine is obviously biased in favor of PCs?but similar results were reported by Mac Addict magazine, in their April 1998 issue?they were almost embarassed at having to report that on some Photoshop functions, the PC outperformed the G3 Mac.
  • Similarly, database tests are almost all much faster on PCs. Not because of hardware, but because the big database software companies have almost entirely ignored the Mac, optimizing their offerings for PCs.

Perhaps this isn?t really the point. While ads showing CPUs on snails make for snappy TV, for most users, hardware has far outstripped typical software. G3 desktop and notebook machines are well-engineered computers, running a solid operating system, with a good range of applications. But while G3 Bytemark benchmark scores outstrip those achieved by similar speed P-IIs, a G3 Macintosh is not ?twice as fast? as a P-II PC (and Apple?s ads carefully do not claim that it is).

Initially, the IBM-Motorola-Apple coalition hoped for wide acceptance of the PowerPC architecture. While most PPCs went into Macintoshes, both Motorola and IBM released PPC machines designed to run Windows NT and Unix. And Mac-clone companies were aiming to produce PPC-based computers that could dual boot between the MacOS and NT, and use inexpensive PC hardware.

But Apple called a halt to the development of such systems, and Microsoft announced that it would not support the PPC for upcoming NT versions, citing low-sales. As a result, the G3 CPU is tightly-tied to Apple-specific designs. But it?s not the end of the road for the PowerPC series.

In May, Motorola announced plans to respond to Intel?s MMX enhancements with new PPC designs. Starting late in 1998, some PPC chips will make use of so-called AltiVec technology. Unveiled at the Spring Networld+Interop conference, these enhancements are expected to go beyond MMX?s multimedia, adding performance for networking and telephony, helping operations ranging from speech recognition to network routers. Fat pipes make it possible to access more data at a time?similar to enhancements already in use in Sun Sparc and Digital/Compaq Alpha CPUs.

On the hardware side, AltiVec ads a vector unit, working in parallel to the integer and floating point units typically found on CPUs. On the software side, there will be 162 new instructions. As with MMX, these will only be usable if both the operating system and applications are written to make use of them. But in theory, at least, a single PPC w. AltiVec could run 30 modems simultaneously.

And IBM?s highly-publicized copper technology will first appear on PPC chips. Using copper wire instead of aluminum to connect transistors will increase speed and efficiency?and will appear in Macs and Mac upgrade cards due later this year. While initial offerings will run at speeds around 400 MHz, it?s expected that this technology, along with 0.18 micron fabrication (and eventual 0.13 micron manufacturing), will permit speeds up to 1 GHz (1000 MHz).

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Alan Zisman is a Vancouver educator, writer, and computer specialist. He can be reached at E-mail Alan