Mac Musings

The January 2003 Power Mac G4 Value Equation

Daniel Knight - 2003.01.29 -

It wasn't completely unexpected that Apple would release speed bumped Power Macs at about this time. The first Power Mac G4 to hit 1 GHz was released on January 28, 2002, the first Macintosh was announced on January 24, 1984, and several other Macs have been released toward the end of January in intervening years.

One number stands out - the Power Mac G4 has now hit 1.42 GHz.

Not So Much Faster

That's less impressive than it sounds, a mere 14% increase in clock speed in the five-and-a-half months since the the dual 1.25 GHz model was released. Moore's Law points to roughly doubling CPU speed every 18 months, which equates to a 25% improvement every six months.

In accordance with Murphy's Law, Motorola has once again failed to keep up with the usual pace of improvement. Last week I noted that Moore's Law points to a fourfold increase over the course of three years, but Motorola only moved the G4 from 450 MHz to 1.25 GHz. With the latest speed bump, we're looking at a 317% increase in clock speed over 3.5 years - Moore's law predicted a fivefold increase (or 400% over base) during the same time period.

Here's a quick comparison of Motorola G4 and Intel Pentium 4 maximum processor speeds and their level of improvement compared with August 1999:

Date Fastest G4 faster than 1999 Fastest Pentium faster than 1999 G4/Pentium
1999.08 450 MHz 600 MHz 75%
2000.02 500 MHz  11% 800 MHz   33% 63%
2001.02  733 MHz  63% 1.3 GHz 117% 56%
2001.07 867 MHz   93% 1.8 GHz 200% 42%
2002.01 1.0 GHz 122% 2.2 GHz 267% 45%
2002.08 1.25 GHz 178% 2.8 GHz 367% 45%
2003.01 1.42 GHz 216%  3.06 GHz 410% 46%

As the above table indicates, Intel has had no problem keeping up with the improvements predicted by Moore's Law. Even if the G4 is in some ways twice as powerful as the Pentium 4 on a MHz basis, the plain truth is that Apple has had to move from CPUs running at 3/4 of Intel's top speed to less than half that, a level Motorola has maintained since Spring 2001.

We are seeing Motorola move a bit closer to Intel. Today's fastest G4 runs at 46% of Intel's to speed vs. the fastest G4 running at only 42% of Intel's speed in July 2001.

Ars Technica

The folks are Ars Technica run one of the few non-Mac tech websites that seems to generally understand and appreciate the Mac. Like us, they realize Apple and the Mac are not without their flaws, but looking at yesterday's comments, I wonder if Hannibal has been spending too much time in the realm of 2-3 GHz machines.

"The FSB still clocks in at a pitiful 167 MHz SDR, and of course the dual-processor machines in the line still use the same old shared-bus topology. (I'm beginning to sound like a broken record on these last two points, but I won't stop griping about them until they're fixed.)"

There's some benefit to improving the ratio between the main system bus and CPU speed, especially at higher multipliers. Running a 2.8 or 3.06 GHz Pentium 4 on a 533 MHz equivalent memory bus keeps your multiplier in the 5-6 range. (The higher the multiplier, the greater the performance hit when the CPU has to access main system memory.)

But the G4 isn't running that fast. When the 1.42 GHz model ships in February it will run at an 8.5 multiplier compared with the 7.5 multiplier on the 1.25 GHz model. The ratio may not be as nice as with the P4, but that's part of the reason for the 2 MB per processor level 3 cache on the high-end machine.

While Apple does use DDR (Double Data Rate) memory in the Power Mac G4, the sad truth is that the current G4 processor can't take advantage of this memory's doubled data rate. We have to wait for a future revision of the G4 before than happens - and then we'll suddenly have the equivalent of a 333 MHz main system bus.

Moving from a shared bus topology to a dual-bus topology would require a complete redesign of the motherboard, which I don't expect to see until Apple moves up to a new generation of CPU. (IBM PowerPC 970 anyone?)

In the final analysis, there are theoretical benefits to a faster system bus, different bus topologies, and making full use of the capabilities of DDR memory, but the Power Mac G4 is already plenty fast as far as most of us are concerned. The expense Apple would have to invest to eke out maybe 5% more performance seem prohibitive and should be postponed until Apple is designing a new motherboard anyhow.

As one person posted in the Ars Technica forum, "What's to complain about faster machines and bigger screens for less money, especially from Apple?"

It's all about productivity and value, not absolute hot rod performance, and that's where the new $2,700 1.42 GHz G4 blows the socks off the old $3,300 1.25 GHz model.


All that said, the new Power Mac G4s represent a great improvement in value, particularly at the top end. So let's start at the top and work our way down.

G4/1.42 GHz

Although the dual processor 1.42 GHz Power Mac G4 represents only a 14% improvement in CPU speed, it also sells for 18% less than the just discontinued dual 1.25 GHz G4. That's a huge value improvement.

For the most part, the new top-end Power Mac is just like the one that replaced it. Same bus speed, same video card, same case, same base setup. Other than a faster CPU, the new model adds AirPort Extreme, Bluetooth, and FireWire 800 ports.

At $2,699, it's the lowest cost top-end Power Mac G4 ever. If you need this kind of power, it's never been more affordable.

G4/1.25 GHz

There are two obvious points of comparison for the new midlevel Power Mac, the just replace dual 1 GHz model and the discontinued dual 1.25 GHz model. At $1,999, it costs far less than either.

While adding AirPort Extreme, Bluetooth, and FireWire 800, the midlevel G4 loses half its cache. Both models we're comparing it to had 2 MB of level 3 cache per CPU; the new model has only 1 MB per CPU. Thus it should offer slightly less performance than the $3,299 G4/1.25 GHz that was Apple's top-end machine a few days ago.

That's impressive value.

G4/1.0 GHz

Apple once again departed from tradition. Where the last series of Power Macs had all included dual processors, the new entry-level Power Mac has a single G4 processor. Under Mac OS X, the operating system and applications can take advantage of dual processors (although not all programs are designed to do so), so it looks like the new 1 GHz Power Mac will provide somewhat less performance than the dual 867 MHz G4 it replaces. (867 MHz x 2 = 1.73 GHz. Less 10% typical overhead yields approximately 1.56 GHz total G4 performance on applications that support both processors.)

On the plus side, the new 1 GHz G4 adds AirPort Extreme, Bluetooth, and FireWire 800 while retailing for only $1,499 - $200 less than the dual G4/867.

Overall Value

But we can't look at value in vacuum; we have to compare the new Power Macs not only with the models they replace at their old prices, but with the discounted prices now being offered on the discontinued models.

Visiting several of the online Apple retailers, I've found the following prices for the "old" Power Macs:

At these prices, I can't see any reason to choose the new single processor 1 GHz G4 over the older dual 867 MHz G4. None. We're looking at 50-70% more computing power for the same price. Grab these while they last.

I can't see any reason to recommend the older 1.0 and 1.25 GHz models at these prices. The new 1.25 GHz model has a smaller level 3 cache and a Combo drive instead of a SuperDrive, but you can upgrade to a SuperDrive for $200 more if you need to burn DVDs.

Dealers are going to have as hard a time unloading these faster two models with these meager price reductions and their poor value as they're having getting rid of first generation 667 MHz PowerBook G4s.

We're also updating the Best Power Mac G4 Deals, which we updated yesterday just hours before the new models were announced, to reflect these changes.