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AMD's Athlon 64 4000+ and FX-55 processors


Rubbing it in
— 12:23 AM on October 19, 2004

AS A CHILD, I loved to play Archon, the chess-like action/strategy game for 8-bit computers. I played often on my Atari 800, and once, I tried playing over at a friend's house on his Commodore 64. He popped the disk into the drive, booted up the computer, and started loading the game. We waited.

And waited.

We went outside, played in an abandoned field, caught some crawdads in the creek, and came back inside. Still loading.

This was the Commodore 64, the computer outselling my beloved Atari 800 by some obscene ratio, the computer my friend had bragged about repeatedly, the computer helping run Atari's home PC business into financial ruin. It must have taken 40 minutes for that game to load via the C64's terminally lethargic 5.25" disk drive. At about minute 39, something deep inside my head must have, silently and imperceptibly, snapped. You are now reading what I believe is the 40th CPU review that I've written for The Tech Report over the course of the last five years. These reviews have been dedicated to the task of providing the reader, with concrete certainty, information about how the most central component in a PC performs across a range of different applications. I suppose it's my way of helping prevent another atrocity like the C64 disk drive situation—or at least of documenting it properly so people know what they're getting into.

The folks at AMD must understand my dysfunction, because they have been producing ever-faster processors to feed my reviewing habit since day one. Today is no different; AMD is lifting the curtain on a pair of new CPUs that are faster than anything else they've ever produced, the Athlon 64 4000+ and Athlon 64 FX-55. As usual, we've run them through a broad spectrum of benchmarks and compared them to their closest competitors, and I can assure you, these things could play one very mean game of Archon, no waiting required.

AMD's new top models
The faster of these two CPUs is the Athlon 64 FX-55. For the uninitiated, the Athlon 64 FX is AMD's image part, one of those super-expensive products that exist to demonstrate to the world what a company is capable of producing. As the new Corvette is to the Chevy Cobalt, so the Athlon 64 FX is to the Athlon 64 3000+. If the FX series has the longest line on the benchmark graphs, the marketers reason, folks will want to purchase the cheaper Athlon 64s. The Athlon 64 FX's foil is the Intel Pentium 4 Extreme Edition processor, Intel's competing image product. Neither of these chips sells in any kind of volume, and they both cost more money than a French diplomat can siphon off of a U.N. oil-for-food program on a slow afternoon. They do, however, cast a halo effect on the rest of their makers' products.


The Athlon 64 FX-55

AMD has committed to providing only one model of FX processor at a time, so the FX-55 supercedes the Athlon 64 FX-53. The difference between the two is all of 200MHz: the FX-53 ran at 2.4GHz, and the FX-55 runs at 2.6GHz. Otherwise, little has changed. The FX-55 still has 1MB of L2 cache, still drops into Socket 939 motherboards, and is still produced on AMD's 130nm fabrication process.

All of that seems pretty simple. The real mind bender is the Athlon 64 4000+, which is basically the same darned thing as the Athlon 64 FX-53: an Athlon 64 processor clocked at 2.4GHz with dual memory channels and 1MB of L2 cache. The only real difference between the 4000+ and the FX-53 is the fact that the 4000+ doesn't share the FX series' unlocked bus speed multiplier for easy overclocking. That's it.

Since the Athlon 64 3800+ has a 512K L2 cache and a 2.4GHz heartbeat, you could be forgiven for expecting the 4000+ to have the same size cache and purr along at 2.6GHz. In fact, AMD may someday introduce just such a product under the 4000+ moniker—AMD has been known to monkey around with its model numbers like that—but today is not that day. If I try to explain all the logic behind AMD's model numbering scheme, not to mention the gaps in logic, I'm liable to start hyperventilating, so instead, I've worked up a quick table that attempts to capture all of the Athlon 64 model numbers to date. It may be incomplete, but I think I've got 'em all. Have a look:

Notice how different bits are traded off as equivalent, so that the move from a single memory channel (on Socket 754) to dual channels (on Socket 939) is considered equivalent to a 200MHz clock speed increase or an additional 512K of L2 cache. Except when it isn't.

No doubt AMD will be making some hay out of the fact that it's introducing a chip rated "4000+" just days after Intel announced it was dropping plans to take the Pentium 4 to 4GHz. However, the Athlon 64 4000+ is obviously just a renamed version of an existing product, so gloating would seem a little inappropriate at this point. Also, you should have a look at the cooler that AMD supplied with our review samples.


The cooler for the FX-55 (left) and AMD's stock cooler for older models (right)

Is this what it takes to get the Athlon 64 FX-55 running comfortably at 2.6GHz? Perhaps not; it may be a little bit of overkill. Still, the outsized heatsink with integrated heatpipes certainly makes one wonder.