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AMD AthlonFX-51 CPU Review
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AMD AthlonFX-51 CPU Review

by hardavenueApril 20, 2016

- Process tech: 130 Nanometer SOI
- Packaging: 940-pin ceramic micro PGA
- 1 HyperTransport link: 6.4GB/s
- Integrated 128bit wide memory controller: 6.4GB/s
- L1 Cache: 128k
- L2 Cache: 1MB
- Die Size: 192mm²
- Frequency: 2.2GHz
- Transistors: 105 Million


- AMD FX-51 2.2GHz CPU (Test Subject)
- Thermaltake Venus 12 cooler
- ASUS SK8N nForce3 Pro150 (Retail, 1001 BIOS)
- 2 x Crucial PC2700 ECC Registered
- 200GB ATA133 Maxtor
- HIS Radeon 9800Pro 128MB IceQ
- Antec TruPower 480W PSU


- Intel 3.2GHz-C (HT disabled, unless otherwise stated)
- Intel Stock Cooler
- Albatron PX865PE Pro II
- 2 x Crucial PC3200
- 200GB ATA133 Maxtor
- HIS Radeon 9800Pro IceQ
- Antec TruPower 480W PSU

The latest AMD Athlon CPU launch has come and gone, with the actual products starting to finally seep through into the market place. As far as the mainstream market goes, two CPU’s were launched – the Athlon64 3200+ and the AthlonFX-51. Both processors feature 64bit processing technology, the first of its kind for the mainstream user, and both promise intense performance beyond our current needs. Whilst 64bit processing is currently useless for 99% of Microsoft Windows PC users, these beasts don’t mind waiting for everyone else to catch up, as they also promise new heights for 32bit performance, something almost everyone can appreciate.

However, from day 1, the FX51 had a few minor problems – nothing technical, rather, its image. For one, it was and still is ultra expensive, which automatically narrows its audience. On top of this, it uses the same pin platform as the Opteron processor, that is, Socket940. Now, server processors like the Opteron don’t really need a future proof platform, because most people serious enough to purchase an Opteron server will probably end up buying a completely new server rather than a new CPU when it comes time to upgrade again. However, this theory doesn’t work for the mainstream performance market, people purchasing this platform with the FX51 are probably doing so for personal use, and it is something they expect will last for some time to come. At the launch, this was not a likely reality, it seemed the Socket 940 platform had seen its fastest CPU on launch, and anyone buying this platform would have to change to Socket 939 for future FX-5X processors.

As it would seem, this is not the definite fate of the Socket 940 platform. Although there is no official confirmation, it was leaked from a rather large roadmap that the FX series will see future additions, from the “San Diego” codename mid next year to the “Toledo” codename in mid 2005. However, there is still no word on which platforms these FX’s will feature. Here is a look at the official AMD roadmap:

amdfx51 amdroadmap


As you can see, the second suggests the Socket 940 platform will see future CPU’s, dubbed the Venus and Denmark, while the San Diego and the Toledo are destined for the Socket 939 platform. Only time will tell which roadmap is most accurate, the official one does not suggest Socket940 will not ever see an upgrade, however, it also doesn’t clearly suggest it will.

Opteron vs FX51: The differences

With both the FX51 and Opteron processors sharing similar architecture, it is hard to differentiate the two from raw performance, rather, it is the features that really separate the two. To start, the Opteron features three HyperTransport links, as opposed to the single link found in the FX51, which further pushes the bandwidth boundary. However the most important difference between the two is probably the SMP capabilities of the Opteron – whilst this is a trivial feature from a hardcore gamers perspective, the Opteron is obviously not for the gamers out there, rather the server market. Both processors could replace one another in their respective markets, and the results probably wouldn’t differ a whole lot, so in reality the FX51 and Opteron are very similar chips with different names for different markets. One characteristic remains however – they both currently cost a heap.

Note the heat spreader – finally AMD users can forget about crushing their CPU cores with improper HSF installation, and boy would that be a disaster on a CPU like the FX51. While on the topic of the cooling, I can also happily note the new style mechanism found with the A64 CPU coolers’s is superb. Incredibly easy to install and uninstall, and almost completely risk free.

Expanding on the specs, it is important to note that the FX51 system’s memory controller is in fact integrated with the CPU, and not in the northbridge as traditionally seen with most modern systems. This 128bit memory controller can push up to 6.4GB/s, and with the HyperTransport and memory bandwidth combined, that’s 12.8GB/s. Certainly nothing to sneeze at.

As for the actual memory itself, the FX51, like the Opteron, requires registered memory, which usually also means ECC (although ECC is not necessarily required). This is expensive memory by default, and you’ll be hard pressed to find registered PC3200, particularly for a reasonable price, so we generally recommend PC2700, like the Crucial PC2700 Registered RAM we reviewed here.


So, I’ve mentioned “HyperTransport” a few times, but what does it mean exactly? Well, don’t get it confused with the “HyperThreading” technology seen with the latest Pentium4’s, which simulates dual processors, HyperTransport is actually the new bus running at 1600MHz for the AMD64 series (Opteron, Athlon64, AthlonFX), producing up to 12.8GB/s for each link (combined with memory bus). What it does is basically replace the multi-level buses found in current systems with a dedicated, high speed and high bandwidth link. An example of this is the PCI bus, however to prevent huge problems with compatibility, HyperTransport is fully compliant with current PCI I/O technologies. As previously mentioned, the FX51 features one of these buses, while the Opteron features 3. For most tasks, 1 is probably more than enough, however it is obviously an advantage for the situations an Opteron CPU is useful for.


AMD Test setup

Due to the fact Microsoft’s 64bit Windows is not currently in final build, we are unable to produce 64bit test environments here, rather, the current 32bit based WindowsXP Professional is our testing environment. This is not a problem, as anyone purchasing this chip right now will probably be running it under WindowsXP or 2000, and even if they did run it under a beta version of Windows 64, they wouldn’t actually be running many applications with 64bit processing. With that said, today we check out the 32bit performance of the FX51 against a 3.2GHz Pentium 4 (note, not the Extreme Edition), however we do plan to pitt this system under the 64bit platform as soon as it has reached true retail status.

amdfx51 sandracpu comparison


In this test, we have enabled HT to showcase how it helps the Pentium4 achieve higher results. Please note however, it is much like comparing a dual CPU setup to a single CPU setup, so the non-HT results are probably showcasing a more accurate “CPU vs CPU” result. The FX51 beats the 3.2-C in both ALU and FPU tests.


amd fx51 sandra multi media comparison



Again, the HT enabled P4 shows considerable improvement, however the Int results show the FX51 beating the 3.2-C even with HyperThreading enabled. Otherwise, the FX51 beats the 3.2C non-HT convincingly.



Specviewperf 7.1


amdfx51 spec viewperf


3DMark CPU

amdfx51 3dmark cpu

By looking at the 3D tests, including SPECViewPerf 7.1’s array of 3d intensive tasks, 3DMark2003 CPU, Comanche4 and UT2003, we see the FX51 has a general lead across the board, besides the 2nd 3DM2k3 CPU test, where the 3.2C beats it by 0.3 FPS. There is no doubting that the FX51 has raw grunt, even at the somewhat real world resolution of 1024×768 it has a considerable lead in both UT2003 tests; a game which use to be very close performance wise across most performance systems.


Like every brand new CPU, the AthlonFX-51 is not for everyone. Actually, the Athlon64 3200+ is the CPU which is not for everyone, the FX-51 is the CPU which is only for very few people; people who need the absolute best disregarding costs. There is no doubting that every dream machine out there should have the FX-51 under the hood, however that is exactly the point – a dream machine. Most gamers can dream, but not many can live that dream, so until the FX51 comes down to a realistic price, it’s really nothing more than an icon for the type of technology we are about to embrace. Unfortunately, there is a little uncertainty about whether or not the Socket 940 platform will see future AthlonFX additions, so if you absolutely must also have great performance with a guaranteed future, the Socket 754 Athlon64 3200+ is probably your best bet right now.

As far as AMD vs Intel goes, the 3.2-C is not exactly the FX51’s competitor, the 3.2 Extreme Edition CPU is, however this CPU was not available for testing at the time of writing so there isn’t much we can do there. From early reviews, it appears the extra cache, the only improvement the P4 EE brings, doesn’t really do a whole lot anyway, so my educated guess would suggest the FX51 reigns supreme as far as performance goes. And don’t forget it has 64bit support, something you’ll probably find handy.

One day.

Note: As for our overall score, we don’t feel one should be given, as the FX51 is really only seeing half its usage until 64bit Windows is mainstream, stay tuned for its release and our return into the world of the AthlonFX.



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