Familiarising ourselves
The name doesn't give much away, save for announcing that it's likely to be faster than the FX-51. A table will be used to highlight the key characteristics of AMD's latest and greatest.| CPU | AMD Athlon 64 FX-53 + | AMD Athlon 64 Model 3400+ | Pentium 4 3.2GHz Prescott | Pentium 4 3.4GHz E.E |
| Clock speed | 2400MHz | 2200MHz | 3200MHz | 3400MHz |
| L1 cache | 128kb | 128kb | 28kb | 20kb |
| L2 cache | 1024kb | 1024kb | 512kb | 512kb |
| L3 cache | - | - | - | 2048kb |
| Memory bandwidth | 6.4GB/s (DDR400) | 3.2GB/s (DDR400) | 6.4GB/s (i875P) | 6.4GB/s (i875P) |
| FSB | 2400MHz (core speed) | 2200MHz (core speed) | 200MHz quad pumped | 200MHz quad pumped |
| Integer pipeline length | 12 | 12 | 31 | 20 |
| CPU Die Size | 193mm² | 193mm² | 112mm² | 237mm² |
| Transistor count | 105.9 million | 105.9mm² | 125 million | 169 million |
| Manufacturing process | 0.13-micron SOI | 0.13-micron SOI | 0.09-micron | 0.13-micron |
| Memory support | DDR400 Dual Channel (Registered) | DDR400 Single Channel | DDR400 Dual Channel | DDR400 Dual Channel |
| OS Support | 32/64-bit | 32/64-bit | 32-bit | 32-bit |
| Voltage | 1.5v | 1.5v | 1.4v | 1.5 - 1.55v |
| Form Factor | 940 | 754 | S478 (for now) | 478 |
| Special features | Registered memory required | Single-channel memory support | SSE3 | 2MB L3 cache |
I've neglected to include either the Athlon 64 FX-51 or Athlon 64 Model 3200+. The reasoning is simple enough; both CPUs only differ from their higher-ranked counterparts on clock speed alone. The FX-51 clocks in at 2.2GHz and the Model 3200+ at 2.0GHz. All AMD has had to do to increase performance on a new architecture is to bump up basic clock speed. FX-51 is a 6-month-old processor now, so adding another ~9% shouldn't have proved too difficult for the Dreseden-based fabrication plant. It's along the lines of what Intel has done with the Extreme Edition line, which now tops out at 3.4GHz.
Just like the Extreme Edition Northwood, the FX-5x range is priced outside the reach of most enthusiasts. At the time of writing both the FX-51 and 3.4GHz Extreme Edition retailed at over £500, but both the AMD Athlon 64 Model 3400+ and Intel Pentium 4 3.4GHz Northwood (non-EE) at just below £300. The price discrepancy between Intel's CPUs can be easily pinpointed to the difference in L3 cache and limited production runs of the more expensive Northwood. AMD's top two K8 processors also only have a few fundamental differences: a brief examination of which should illuminate the finer points of the FX-53 and provide a base for understanding the benchmarks that will follow. I'm not going to discuss te FX-53's technical attributes individually. That was done here.
Clock, memory and controller differences
The most obvious difference is with respect to clock speed. FX-51s and Model 3400s clock in at 2.2GHz. The FX-53 simply raises that speed to 2.4GHz, so with all other things remaining equal, it has to be a faster processor. Things aren't that equal, really. Both Sledgehammer (FX-5x) and Clawhammer (Model 3xxx) feature on-die memory controllers that directly communicate with system memory, thus leaving out the usual Northbridge route. That has the benefit of reducing latency greatly, as the largest latencies are incurred in getting information into and out of the bridge and to the CPU. The Sledgehammer incorporates 2 64-bit memory controllers as opposed to the Clawhammer's single 64-bit controller. Crucially both controllers work at core speed.
Factoring in equal RAM timings and comparing results to a tuned i875P chipset we have seen that AMD's 64-bit CPUs knock off up to 40ns of overall memory latency. What convolutes the issue is the Sledgehammer's (FX-5x) use of registered memory. The reasoning here is also again simple. The Sledgehammers, taking their cue directly from the Opteron line, are designed to be used in instances where data integrity is critical. The upshot of that is the lack of extremely low-latency modules (read performance) that are currently available, although the likes of Corsair and OCZ are doing their best to rectify this. What this means to performance is a smaller-than-expected performance gap between AMD's Sledge and Clawhammer CPUs.
Packaging and cache levels - how it will become confusing
The extra pins for an added memory channel manifests itself into the Sledgehammer CPU having 940 pins whilst the Clawhammer makes do with 'only' 754. You'd think that would be that. AMD's going to cloud the whole identifying issue by moving both the Sledgehammer and Clawhammer CPU ranges on to a 939-pin format, yet it will also keep a higher-clocked Sledgehammer on the existing 754-pin format. Ryszard explains it all here. Note how the Clawhammer's cache levels are subject to what seems like arbitrary chopping.
Probable performance can be summed up in a simple sentence - The FX-53 will be fast because the FX-51 was. All the ingredients are in place to ensure excellent performance. Our only unknown is how it will compare to the latest Pentium 4 batches and AMD's own beefed-up Model 3400+ Clawhammer.
