- Introduction

Last month we examined the Athlon 64 3800+, a high definition 64-bit state-of-the-art processor from AMD. Since then, AMD has introduced two more processors. The first is the Athlon 64 4000+ which is the successor to the 3800+ and the second, the Athlon FX-55, which we'll be reviewing here.

So what is the real difference between the two family lines, Athlon 64 FX and Athlon 64?

Initially, the difference was quite obvious. The FX processors used the 940-pin socket type whereas the 64 was made for the 754 socket. The FX required the more expensive, yet reliable buffered memory when the 64 could run just fine with plain unbuffered modules. Also, the FX usually had more L2 cache memory and generally ran at higher clock speeds.

However, AMD then introduced us to the 939 socket and having decided to base all of its processors on this socket, the fine line between the two families began to blur. Now it's almost impossible to spot the difference. The 4000+ and 3700+ offer 1Mb of L2 cache and if you compare the two top products from each family, you'll see that the only thing seperating them is 200MHz clock speed. AMD's Athlon 64 4000+ is just an FX-53 with a different name!

Socket 939

Actually, there's another not so obvious difference between them. All Athlon 64 processors ship with their CPU multiplier locked, as opposed to the FX processors that are still left unlocked by AMD.

Athlon 64 FX processor architecture

Let's examine the FX-55 features more thoroughly.