Introduction

AMD has had no problems announcing new CPUs during the latter half of this year, in the past three months we’ve seen four new releases, the Athlon XP 2400+, 2600+, 2700+ and 2800+. Unfortunately, purchasing these CPUs has been rather difficult, supplies of the Athlon XP 2400+ were dry up until roughly a month ago, while the 2600+ and 2700+ have only become available within the past few weeks.


This has been a little frustrating for consumers in the market for a new CPU, as these chips are no slouches when it comes to performance and are priced to move. Part of the problem originates from AMD’s difficulties with its new 0.13-micron manufacturing process. While AMD practically executed flawlessly at 0.18-micron, they got off to a shaky start at 0.13. The first chip based on the process, the Athlon XP 2200+, hardly scaled beyond its initial clock speed of 1.8GHz. Meanwhile, Intel had no problems cranking up the clock speed of its Pentium 4 processors.

In response, AMD implemented a few changes to its 0.13-micron cores in order to enable higher clock speeds on these processors. An additional metal layer was added to the Thoroughbred core, giving the new chip a total of nine layers. To reduce electromagnetic interference, additional decoupling capacitors were added. Finally, the circuit paths within the processor were optimized. As a result of these changes, the die of the chip is a little bigger and the transistor count increased slightly, so these chips are physically more expensive to produce, but if AMD is able to increase its yields as a result of these changes, the added expense pays for itself.

But that’s not the only thing AMD has done to spice up its Athlon XP line, it has also implemented a 333MHz bus on its Athlon XP 2700+ and 2800+ processors. By moving to a 333MHz bus, bandwidth to the processor increases from 2.1GB/sec to 2.7GB/sec, a 22% increase. This is significant because as clock speeds continue to rise, the processor spends more time idling as it waits to retrieve data from main memory. By increasing the bus speed, the processor is better fed, increasing its efficiency. Another positive is that the processor and memory bus now operate in synch, reducing latency.

So where does a 333MHz Athlon XP 2600+ fit in with all of this? By utilizing a 333MHz bus, AMD can produce a processor that performs similarly to the original 2600+, but at the same time it operates a lower clock speed. Right now demand for the 2600+ exceeds its supply, so by producing a 333MHz 2600+ chip, AMD is able to fill the OEM and retail channels with more processors. During testing we found that the 333MHz Athlon XP 2600+ is also a little faster than its 266MHz predecessor, another bonus!