Jul 9, 2004

The Ninety Nanonmeter Speed-Bump

Last Summer, Apple launched a serious upgrade with the Power Mac G5 and for the first time in a decade used a totally new PowerPC core not based on the PowerPC 603. With IBM's PowerPC 970, Apple is using a mainframe-level chip capable of massive parallel computing, access to hyper bus speed, and huge volumes of cache. Since the industry hit the wall shrinking to 90nm, however, the Mac community has expressed unrest at the clock-starvation: Memories of Motorola's 500 MHz Fiasco five years ago bubble up to the surface.

Kill your worry processes, Mac users. There's no clock-stall in the PowerPC's future any time soon. Motorola's failure to achieve speeds above 500 MHz was a result of it recycling the PowerPC 603 core far too many times, something that IBM avoids in using its Power series core. The speed-bump at 2.5 GHz is the result of a one-shot problem involved in shrinking the die. But let me explain in more detail.

The PowerPC 603 started life at 50 MHz but after reaching 100 MHz Motorola doubled its L2 cache and shrank the die due to niggardly performance. It tapped out at 300 MHz before receiving the backside cache of the PowerPC 620 to become the G3. By this time, however, the core was already three years old and the advancements put into the G3 dropped the clock back to 233 MHz.

ChipDebutInitial ClockMax Clock
PowerPC 6031994 50 MHz300 MHz
PowerPC G31997233 MHz450 MHz
PowerPC G41999350 MHz533 MHz
PowerPC G4+2001667 MHz1,300 MHz

Table 1 The PowerPC 603 and its descendants.

The G3 had reached 450 MHz when Motorola added a better FPU and AltiVec to it thus bringing the PowerPC G4 to market. Again the addition of new technology dropped the clock, this time down to 350 MHz. The net result was a whopping gain of 300 MHz over the span of six years. At this point the G4 lost steam at 500 MHz and wouldn't surpass that speed for 18 months.

Unlike the 603 line, IBM's PowerPC 970 is based on the Power4 mainframe design. Without being hobbled by adding new technology to an aging, creaky core, IBM is able to outline the PowerPC 980 and 990 processors for Apple today as it's beginning work on taping out the Power5. Unlike Motorola's lethargic climb up the megahertz ladder, IBM confidentally expects to hit 10 GHz with the PowerPC 990 in mid-2008.

PowerPowerPCAppleInitial ClockMax Clock
Power4PowerPC 970G51.4 GHz3.0 GHz
Power5PowerPC 980G63.0 GHz6.0 GHz
Power6PowerPC 990G76.0 GHz10.0 GHz

Table 2 IBM PowerPC roadmap.

Also keep in mind that the slowdown is industry-wide. Cores from AMD, Intel, MIPS, Sun, and others are all experiencing unexpected problems in the transition down to 90nm. Unlike Motorola's failure to innovate, all chips companies bear the brunt of the shrinkage which has everything to do with electrical limitations and nothing to do with business decisions. Rest assured that IBM hasn't lost its edge. In fact, IBM is already shaping up to be the industry leader again as its points the way past these problems.

Apple zealots have nothing to fear as the industry trudges forward through the 90nm quagmire. Mac users also have the most to look forward to as the PowerPC line has the most room for performance enhancement out of any of the architectures involved in the recent slowdown. Not only will IBM be first out of the gate soon, but will have the fastest horse on which to ride — which means Mac has the greatest benefit to reap from this slowdown.

Put on your seat-belts and hold on tight, Mac fans. Apple's putting the peddle to the floor out of the gate and there's no telling where they'll bury the needle.

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