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
Or others from Apple Corporation, all ending with the same claim?that
G3 PowerPC CPU in Apple?s Macintosh computers is up to twice as
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,
showed off a couple of demonstrations aimed at proving the point. He
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
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
There?s no doubt about it?from the beginning, the
designed by IBM, and built by Motorola, is a powerful CPU. It uses a
design that is in many ways more efficient than the 80x86 design that
has steadily evolved since the 1970s. And the G3 (for Third Generation)
PPC was the first series designed specifically for Apple hardware. At
same time, Apple?s operating system has steadily become more ?PowerPC
The result is a processor and operating system that are, to a large
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
L1 cache, built into the CPU, and 1 meg of L2 cache?in both cases,
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
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,
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
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
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
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
run-of-the-mill hardware). And on the software used. Microsoft Office
for n example, was well known as an inefficient slowpoke on the Mac,
its replacement, Office 98, includes ?quick loading code? that is a
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
They tested a number of functions in Adobe Photoshop 4.0.1: Resize,
Blur, Unsharpen Mask, Lighting Effects, and Rotate, on a 10 meg TIF
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
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
similar results were reported by Mac Addict magazine, in their April
issue?they were almost embarassed at having to report that on some
functions, the PC outperformed the G3 Mac.
- Similarly, database tests are almost all much
faster on PCs. Not
of hardware, but because the big database software companies have
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
software. G3 desktop and notebook machines are well-engineered
running a solid operating system, with a good range of applications.
while G3 Bytemark benchmark scores outstrip those achieved by similar
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
of the PowerPC architecture. While most PPCs went into Macintoshes,
Motorola and IBM released PPC machines designed to run Windows NT and
And Mac-clone companies were aiming to produce PPC-based computers that
could dual boot between the MacOS and NT, and use inexpensive PC
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,
low-sales. As a result, the G3 CPU is tightly-tied to Apple-specific
But it?s not the end of the road for the PowerPC series.
In May, Motorola announced plans to respond to Intel?s
with new PPC designs. Starting late in 1998, some PPC chips will make
of so-called AltiVec technology. Unveiled at the Spring
conference, these enhancements are expected to go beyond MMX?s
adding performance for networking and telephony, helping operations
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
only be usable if both the operating system and applications are
to make use of them. But in theory, at least, a single PPC w. AltiVec
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
increase speed and efficiency?and will appear in Macs and Mac upgrade
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
(and eventual 0.13 micron manufacturing), will permit speeds up to 1