AMD Athlon64 and Athlon64 FX

Only a couple of Chips have been released so far as you can see by the table below. Not that the Athlon64 does not have the standard FSB as with all the other CPU's but uses a hyper Transport link. The clock frequencies of the Athlon 64 do not always seem to go in order with the model numbers but other factors such as Level 2 cache do come into play when AMD calculate the model numbers.

A special point about the Athlon64 is that it has an on-board memory controller. It deals with the system memory direct and does not have to go via the chipset. This means there is no external Front side bus as such, but a solitary Hyper Transport link. The fact that only one link exists and not 3 as in the Opteron means that there is not chance for any Multiprocessor support with the Athlon64. This is not that AMD will not be supporting it, its an impossibility from the design.

The Athlon64-FX

The Athlon64 also comes in an FX flavour. the difference between the two chips is the dual channel memory controller. The Athlon 64 uses a single channel memory controller. There is a downside to the FX version of the chip though, the Athlon64- FX needs to used registered RAM modules where as the Athlon64 can use everyday unbuffered DIMM's. The Athlon64 FX was born really out of necessity. Intel had a working Dual Channel chip already and AMD could not be left behind. They had borrowed the design from the server CPU named Opteron and added support for the DDR 400 memory to make it desktop compatible. It was the fastest way to achieve their goal. the initial version of the Athlon64 FX is very rushed and its likely to be altered as soon as a new version comes out. Changes will include added support for Unbuffered DIMM's and a different Pin-out on the chip.

Motherboard support for the Athlon64 FX has been initially limited while there are many boards supporting the Athlon64

64-bit - How will this improve performance?

Well we have heard that this great new CPU supports 64-bit processes and is all marvellous and wonderful, but how does moving to 64-bit actually help the end user. Currently all the Apps that you are using are 32-bit, the operating system you are likely to be using is also 32-bit. So at the moment the benefits are minimal. Obviously the CPU will work and is faster than the Athlon XP's of any kind. bit in the 32-bit world the only real benefit is the onboard memory controller and higher clock speeds, these have nothing to do with the 64-bit nature of the CPU.

The release of Win64 or whatever Microsoft decide they wish to call it, will alter things round a little bit. Currently you have a memory limit of 4Gb set by Windows, however only 2Gb of this can be used by a single process, Windows reserves anything over this. By using the Athlon64 CPU your 32-bit applications will be able to utilize the full 4Gb of memory available to it. High memory tasks will run a great deal more smoothly. 32-bit applications would have to be patched in order to use this however. This does rely on the software companies updating their programs and releasing a patch.

The scenario that the manufacturers are trying to get to is running a 64-bit application under a 64-bit OS, here the OS would allocate all the available memory and the Apps would have more registers to utilise. The expectation is that for non-memory bound applications you will see an increase of about 10-20% for memory bound applications (Apps limited by the memory you have available) The process will me much more efficient. Less swapping to hard disk and more information stored directly in memory.

This release from AMD is a completely new design, away from the K7 we go and into the 64-Bit world of the K8. It has to be said that its most useful features are not available to us at the moment with the limitations being that today's Operating systems and applications are all 32-bit. There are plans already to change this however.

The fact that this 64-bit CPU supports 32-bit processes means that upgrading to this CPU is certainly not a problem. Bear in mind however that if you purchase the FX version of the chip you will have to have Registered DIMM's until a further release is made.

The memory controller being on the chip is a unique feature which allows  the CPU to communicate with the RAM directly without the need to go through the chipset. I believe this to be the most important feature for use today. A good upgrade if you plan on moving to 64-bit OS's and applications on there release, a bit expensive if you are planning on staying with your current windows for a few years to come.

Technical Features