Pentium 4 Northwood
The chip code-named Northwood is Intel's second incarnation of the Pentium 4 processor. The Pentium 4 "Northwood" isn't fundamentally different from the original Pentium 4 "Willamette," but there are a couple of significant changes to the chip.

First, Intel has changed the manufacturing process used to fabricate the chip. The first Pentium 4 chips were manufactured using Intel's 0.18-micron fab process, which used conventional aluminum for the chip's interconnects. Northwood is made on Intel's new 0.13-micron process, which features copper interconnects with a low-K dilectric material that reduces crosstalk. Intel claims its 60-nanometer transistors are the world's smallest and fastest in volume production, as well. The Pentium III made the conversion to this new manufacturing process a number of months ago, and the Pentium 4 is just now making the move.

This so-called die shrink does several things for the Pentium 4. Northwood is smaller, runs cooler, and requires less power than Willamette. The Pentium 4's die size shrinks from 217 square millimeters to 145 square millimeters. Because Intel can fit more chips on a wafer, Northwood should be cheaper to manufacture. The process shrink should also enable Northwood to run at even higher clock frequencies with ease.

The die shrink also made room for Intel to increase the size of the Pentium 4's on-chip level 2 cache from 256K to 512K. This extra cache takes the Pentium 4 from 42 million transistors to 55 million. The jumbo-sized L2 cache ought to help Northwood tackle the Pentium 4's big bugaboo: low clock-for-clock performance. A larger cache should help keep the P4's deep instruction pipelined fed, increasing the number of instructions per clock (IPC) the chip can execute.

Intel is introducing Northwood at two initial clock speeds: 2.0GHz and 2.2GHz. In order to differentiate the Northwood 2GHz from the older Pentium 4 "Willamette" 2GHz, Intel is calling the Northwood 2GHz the "Pentium 4 processor at 2.0 'A' GHz." The "A" designation will conjure up warmly remembered visions of the Celeron 300A for old-timers like me, while the rest of you will probably be wondering why Intel couldn't come up with a better name than "2.0 'A' GHz."

The Athlon XP 2000+
The Athlon XP 2000+ is simply AMD's latest speed ramp of the Athlon XP. Like all Athlon XPs, this new one gets a model number that's independent of its clock speed. The previous top speed for the Athlon XP was the 1900+ model, which runs at 1.6GHz. (We reviewed the 1900+ here.) The Athlon XP 2000+ runs at 1.67GHz.

The Athlon XP hasn't yet undergone the die shrink to 0.13 microns. Like Northwood and unlike Willamette, however, that Athlon XP is made with copper interconnects, which AMD has been using on Athlon chips for quite some time now. AMD has plans to take the Athlon line to 0.13 microns this quarter; that chip is code-named Thoroughbred. However, even without the die shrink, the Athlon XP is only 128 square millimeters. Because Athlon XPs are made up of only 37.5 million transistors, they're much smaller than the Pentium 4—even smaller than die-shrunk Northwood. All other things being equal, Athlon XPs ought to be cheaper to make, as well.

Don't be fooled by the Athlon XP's relatively pokey 1.67GHz clock speed. There's a reason AMD puts that model number label on its CPUs; they perform quite a bit better, clock for clock, than the Pentium 4.