AMD's Athlon 64 FX-51

The Athlon 64 FX-51 Processor
AMD Drops the Hammer, On Your Desktop!

By, Marco Chiappetta
And Dave Altavilla
September 23, 2003

We're sure some of you are interested in knowing just how much overclocking headroom there is in the Athlon 64 FX-51.  As we mentioned earlier, the FX-51's default clock speed is 2.2GHz.  Due to the fact that the memory controller has been integrated at the CPU chip level with the Athlon 64 FX-51 architecture, it too runs at 2.2GHz.  As you raise the speed of the external clock generator used on the motherboard, to derive the processor's operating frequency, you end up overclocking the CPU and memory controller concurrently.  Ultimately, the results are similar to what happens with more "traditional" systems that have their memory controller integrated into the Northbridge; the CPU and Memory run at higher speeds. 

With the Athlon 64 FX-51 (and Athlon 64 or Opteron) however, there is a chance that your overclocking efforts may be limited by memory controller's ability to operate at these higher speeds.  This adds another layer of complexity to the overclocking process.  Also keep in mind that Registered DIMMs, rated for high-frequency operation are much harder to come by, versus standard modules.  So overclocking the FX-51 specifically may be a bit tougher than you might be use to (the standard Athlon 64 does not require Registered DIMMs).  Luckily, like recent P4 boards, through the use if divisors, most Athlon 64 motherboards will have the ability to run system memory at lower speeds, while overclocking the CPU.  If you find your DIMMs have trouble running at speeds over 200MHz (PC3200 - DDR400), you can raise the divisor and run the memory at 166MHz (PC2700 - DDR333).  We tried overclocking our Athlon 64 FX-51 based test system at multiple memory speeds, but unfortunately we didn't have much luck...

Overclocking the AMD Athlon 64 FX-51 Not Much To Report...Yet.

The maximum clock speed we were able to hit with our FX-51 test system was 2343MHz, an modest increase of only 143MHz.  We could not get the test system higher than 2343MHz regardless of what speed we ran the memory.  We tried setting the memory to operate at 333MHz, and even 266MHz, but couldn't get the system to overclock any higher.  We think our particular CPU was capable of more, but unfortunately, the Asus SK8N motherboard we used for testing was not up to the task.  With the clock generator set to anything higher than 213MHz, upon exiting the BIOS and re-booting, we were greeted with a message saying our BIOS image was corrupt and needed to be repaired.  We re-ran SANDRA's CPU, Memory and Multimedia benchmarks, while the system was overclocked and were most impressed by the Memory bandwidth results.  With a relatively small bump in clock speed, the FX-51 test system almost broke the 6GB/s barrier!

Even though we did not have great success overclocking our particular test system, this does not necessarily mean the FX-51, or other Athlon 64s for that matter, are not going to be "overclocker friendly".  When initially released, the FX-51 will still be built using ceramic packaging (the Athlon 64 is using organic packaging similar to the current Athlon XPs).  Seeing the FX-51 in its current form, approach the 2.4GHz mark is very promising.  With further enhancements to their manufacturing process, AMD should be able to release higher clocked FX series CPUs with relative ease.

We should also mention that the multiplier adjustments we all enjoyed with the Athlon XP line of processors seem to be a thing of the past.  Currently, Athlon 64s are not easily modifiable to allow multiplier adjustments (The FX may ship unlocked, but we could not verify this with the SK8N), and it is not clear whether we will ever be able to.  Many core elements from the Athlon XP carried over into the Athlon 64, however.  So there may be a way to alter the multiplier, hidden in a white paper somewhere.  Time will tell.

After spending some time with the AMD Athlon 64 FX-51, it's safe to say we were definitely very impressed with AMD's new platform and CPU.  In addition, our benchmarks have proven that Intel's Pentium 4 Extreme Edition offers up some fierce competition and that the addition of 2MB of L3 cache, gave the P4 a significant and much needed boost.  It's impossible to make a blanket statement and declare one CPU "better" than the other, but in the benchmarks that matter most to our audience and the readers here at HotHardware, the Athlon 64 FX-51 was clearly the faster CPU.  The Athlon FX-51 won a majority of the gaming benchmarks and totally dominated the Business and Content Creation tests.  From a performance perspective, the Athlon 64 FX-51 is undeniably a success.  This CPU performed extremely well in our standard suite of 32-Bit benchmarks, and promises future performance gains and functionality through the use of 64-Bit operating systems and applications.

The Athlon 64 FX-51 may be one of the highest performing desktop CPUs around right now, but it will not be as widely available as the Athlon 64 3200+, which is also being officially unveiled today, along with a few mobile variants.  We recently got our hands on an Athlon 64 3200+, but unfortunately it was too late to thoroughly test it and include in this article.  Initial reports put it's performance about 3-8% behind the FX-51, which still places it near the poll position of the Desktop Processor pack.  It won't put up the kind of numbers that the FX-51 can.  However, the Athlon 64 3200+ can still beat or remain competitive with a 3.2GHz P4 in most benchmarks, which is exactly the type of product that AMD needs in their mainstream CPU line-up.  With the Athlon 64 3200+ clocked at "only" 2GHz at launch, we expect AMD will be able to ramp clock speeds up to 2.2GHz, or higher, relatively easily.  Don't be surprised if you see an Athlon 64 3400+ released sometime in the not so distant future.

At the moment, the $733 Athlon 64 FX-51 will be more expensive than a standard 3.2GHz P4 ($607), but priced at right about the same level as the 3.2GHz P4 Extreme Edition ($740).  However, the Athlon 64 3200+ at $417, is currently almost $200 less than a standard 3.2GHz P4, making it an attractive choice for someone looking to build a high-end PC, who doesn't need the absolute fastest machine on the block.  Street prices will almost certainly dip below these levels, but we suspect the Athlon 64 will still command a premium price for quite a while.  With a die almost twice the size of a Barton based Athlon XP, producing these CPUs cannot be cheap.  AMD will surely keep prices stable, until they absolutely have to lower them to remain competitive.

AMD tells us they will have P.I.B. (Processor In a Box) availability and that system builders will be able to place orders as of today.  They also expect a "normal" processor ramp to volume.  If you're eager to get your hands on one of these CPUs, they should be available at your favorite retailer shortly.  (Update: It has only been a week since the launch of the Athlon 64 & FX-51, and they are already available from multiple vendors.  The P4 EE, however, is nowhere to be found.)     940-Pin and 754-Pin motherboards based on NVIDIA and VIA chipsets are also already available, so AMD fans who've been waiting for the Athlon 64 should have an assortment of hardware to choose from.  From the looks of it, AMD is right back in the game with the "enthusiast" performance PC crowd.  Not that they ever formally left the arena but it has been a fairly long dry spell, since the time AMD could claim a Desktop Processor performance edge over Intel.  The tables certainly have turned a bit however for AMD, as of this fine day in September 2003.  We can almost feel the deluge of Motherboards, Heat Sinks and assorted Athlon FX-51 and Athlon 64 supporting products, coming into the lab here.  AMD has "got game" again in a very literal and figurative sense.  Then again, we're expecting Prescott to arrive sometime in Q4.  Sleep?  Who needs it.  We'll keep the cold cathode light burning here in the lab, so stay with us.

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