MaximumPC 2006 12

W

hoever said that technology just gets cheaper and better should have

his or her name on a plaque somewhere in Silicon Valley; because,

baby, technology just got cheaper and better.

Intel’s Core 2 Extreme QX6800 steps up the pure PC-power arms race by

offering four execution cores in a single CPU. Just two years ago, the only

place you’d fi nd such a beast would be in a midrange server box or a high-end

workstation. But today you’ll fi nd four-in-one procs in average-Joe PCs or on

the shelves of the local screwdriver shack, at civilian prices.

We take a tricorder to Intel’s new processor to answer the burning question:

Is quad core right for you?

BY GORDON MAH UNG

QWhat else does Intel get from using

this method?

ABesides getting quad core now, the

two-dies-tied-together strategy also helps

Intel keep costs a little lower. If the chip

were a monolithic die, every single core on

the die would have to run at 2.66GHz

for it to be viable. Because there’s always

the potential for defects in any die that

comes off the production line, such a strat-

egy would lower the overall yield of the

chips. By using separate chips, Intel can

hunt through its production run for two

dual-core chips that run at 2.66GHz, which

is much easier and cheaper. It’s a little like

hunting for a four-leaf clover. If you could

engineer the ability to take two two-leaf

clovers and join them together, you could

farm a hell of a lot more four-leaf clovers

than the poor sap combing the fi elds on

DECEMBER 2006 MAXIMUMPC 49

Power!

Quad

QGreat Zeus! How did Intel make a quad-core CPU so

quickly after producing its last CPU?

AIntel did it using a little trick it learned when making the Presler

version of the Pentium D processor. Unlike the company’s original

Smithfi eld Pentium D that featured a monolithic dual core—two

cores on a single contiguous piece of silicon—Intel was able to put

two single-core Presler chips inside the same CPU package and

connect them after the fact. With the Core 2 QX6800, Intel takes

two dual-core Core 2 pieces of silicon and connects them inside the

CPU package to create a quad core.

Head spinning? Think of the quad-core QX6800 as two separate

islands, each with two cities. A single bridge (the front-side bus)

connects both the islands to the rest of the world (the mobo chip-

set). The cities on each island know about each other, and residents

can pass from City 1 to City 2 at relatively good speeds, but if a resi-

dent wants to visit City 3 or City 4, he has to drive across the bridge

and make a U-turn through the chipset before heading back over

the bridge to the other island.

AMD has stuck with a monolithic die approach (where all four cities

are joined on the same island and interconnected) and has slammed

Intel’s approach as a hack. Intel responds that it doesn’t matter how

you deliver the quad cores, just as long as you do. In other words:

Would you rather have quad core today at the same price as a dual-

core processor or would you rather wait until the end of next year?

It’s worth noting that putting both cores on the same piece of

silicon is meaningless if it isn’t done right. Intel’s original Pentium

D Smithfi eld was a monolithic dual core, but those cores too

could only communicate via the front-side bus. It was like build-

ing two cities next to each other with an impervious wall running

down the center.

Front-side bus to the motherboard chipset

CORE 2

CORE 1 CORE 3

CORE 4

QUAD CORE: HOW IT WORKS

The two dual-core chips that form the quad QX6800 commu-

nicate with each other by circuitous means.