Thunder Over Sunnyvale:  AMD’s Unleashed Athlon 64 and FX-51 Battle Intel’s Pentium 4 "Extreme Edition." 

After four years of endless speculation, anticipation, and frustration, AMD’s long-awaited Athlon 64 and Athlon 64 FX-51 are here. Those of you interested in the road to K8 and the history of K7 can check out our look back here, otherwise it’s onward to Hammer.

K7 is Dead, Long Live K7:

When planning K8 four years ago AMD had two options:  They could either extend and improve the basic K7 architecture further, betting on its ability to remain a competitive design, or they could take the route Intel took with the Pentium 4 and design a new core from the ground up.  AMD chose the former, and it?s a good thing they did, as moving to SOI and creating the new AMD64 extensions was obviously problematic enough without attempting to build an entirely new class of processor at the same time.

Two factors that will be of interest to anyone who remembers the utter hell of mounting original Athlon heatsinks--all Athlon 64 chips now ship with a heatspreader and sophisticated on-die thermal protection equivalent to that of the P4.  The heatsink mount system has also been re-engineered for easier application (and no longer any problems slamming a screwdriver into one’s motherboard).

AMD did make several adjustments to Athlon’s core design while re-engineering it for Hammer.  K8 features a better branch predictor than AthlonXP, as well as a larger set of TLB’s (Translation Look-Aside Buffers), both changes that should improve the CPU’s efficiency.  AMD also added an additional two stages to the Athlon’s 10-stage pipe, for a total of 12.  This should allow the Athlon 64 and Opteron designs to scale better than the original AthlonXP could, while keeping the IPC-cost minimal.  Finally, AMD added full SSE2 support to Hammer, a move which should strengthen the core in several tests that formerly favored the P4.

The two main changes introduced by Hammer, of course, are its integrated memory controller and support for the AMD64 instruction set.  Both have been discussed extensively both by us and others, but we will touch on both again.

Until now, the memory controller has always been housed on the motherboard itself, where it interfaced with the CPU via the FSB and ran at the same speed as that bus?400 MHz on the nForce2, 800 MHz on the P4 i875, etc.  By integrating the memory controller into the processor itself, AMD is able to accelerate it to full processor speed?2.2 GHz in the case of Athlon FX-51.  This drastically cuts memory latency.  The benefits to an on-board memory controller are immediately obvious, but choosing to go this route has also presented AMD with some unique challenges, which we’ll discuss later in the review.

 
AMD’s K8 Architecture--note that the DDR Memory Controller and Hyper Transport Links both essentially "hang off" the processor.  This allows for easier upgrades to the controller.

The final addition to the Athlon 64 / Opteron core was, of course, the x86-64 instruction set itself.  By offering full backward compatibility with existing 32-bit code along with 64-bit capability for future x86 software, AMD hopes the market will embrace its produce as a simultaneous means of gaining high-performance 32-bit hardware along with future 64-bit compatibility.  Because there is very little AMD64 software on the market today we’ll primarily be examining Athlon 64’s performance in 32-bit code, but we will touch on future 64-bit performance as well.

The heart of the Hammer core, therefore, is a highly-optimized and efficiency-boosted K7 with a low-latency on-die memory controller and support for what AMD hopes will become the new architecture standard of the 21st century.  It’s impressive?but is it strong enough to take on Intel? 

next >

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• AMD's Plan of Attack (1 of 18)
• Questions on AMD64 (2 of 18)
• The Intel Pentium 4 "Extreme Edition" (3 of 18)
• The Combatants (4 of 18)
• Test Setup and Configuration (5 of 18)
• Synthetic Tests (6 of 18)
• Office Performance (7 of 18)
• Office Performance (Cont) (8 of 18)
• MP3 / DVD Encoding (9 of 18)
• 3D Rendering (10 of 18)
• 3D Rendering, Cont (11 of 18)
• Gaming (12 of 18)
• Gaming: Unreal Tournament (13 of 18)
• High-end Gaming Quality Tests (14 of 18)
• Performance in a Nutshell (15 of 18)
• Other Important Factors (16 of 18)
• Overall Winner, Conclusion (17 of 18)
• Addendum, 64-bit Performance (18 of 18)