Sigh, the Athlon 64 FX

With the release of the 865PE and 865G chipsets, Intel has ensured that virtually all Pentium 4 processors on the market are paired with very high-bandwidth dual-channel memory subsystems. Ignoring the performance boost Intel gains by going to dual-channel, OEMs demanded a dual-channel solution from AMD simply as a checkbox feature.

Not having the time or resources to undertake introducing a brand new dual-channel desktop processor, AMD simply took their existing dual-channel design and called it an Athlon 64 FX. The existing design was the Opteron of course, and the first incarnation of the Athlon 64 FX is almost directly borrowed from the Opteron. What do we mean by directly borrowed?

For starters, the Athlon 64 FX gets the Opteron's memory controller with a slight change - support for DDR400. Offering DDR400 support on the server side is a little trickier than on the desktop for a couple of reasons; server processors must go through more validation than their desktop counterparts and adding DDR400 to the list of validated configurations would increase testing time. Then there's the issue of bringing DDR400 support to motherboards; an issue whose complexity increases tremendously as the number of memory slots you have to support grows. Given the memory requirements of the server market (and associated memory slots), it's just easier to wait on DDR400 support.

On the desktop, DDR400 support is great and the 128-bit memory controller from the Opteron is also nice to have, however there is one issue with the Opteron's memory controller that made its way to the desktop - the memory controller only supports buffered (aka registered) DIMMs. Although AMD is launching with Kingston releasing a line of HyperX registered DDR400 DIMMs, the vast majority of the desktop users have invested in unbuffered DDR400 DIMMs and spending more on registered DIMMs isn't exactly an easy pill to swallow.

AMD's justification for no unbuffered support is that the Athlon 64 FX is for the "enthusiast" community and these "enthusiasts" will want to use lots of memory of densities that are currently only available in registered module sizes. Given that very few "enthusiasts" have registered DDR400 it seems much more likely that it was simply easier to re-badge the Opteron than modify the CPU to support unbuffered memory.

What is necessary to add unbuffered support? Unfortunately, it is a CPU packaging issue and not something that can be added on the motherboard (remember, the memory controller is on-die now). AMD plans on adding unbuffered support to the Athlon 64 FX, but that will come at a later date as they will have to redo the chip's packaging. It seems likely that AMD would introduce unbuffered support with the rumored 939-pin Athlon 64 FX due out next year since they are changing the package anyways to support a different pinout.

Although AMD says that the Athlon 64 FX is for use in single processor environments only, the current version appears to have all three Hyper Transport links - meaning that it can work in multiprocessor environments just like the Opteron. AMD has indicated that future versions of the Athlon 64 FX would only have a single Hyper Transport link, but there's no way of knowing when that will be.

With the Athlon 64 FX, AMD has abandoned their model number system in favor of a series nomenclature similar to the Opteron. For example, the first Athlon 64 FX is the series 51 CPU, running at 2.2GHz. The number 51 was chosen arbitrarily (AMD confirmed this) and indicates nothing about its performance relative to any chip other than the Athlon 64 FX. The next CPU due out next year will be the Athlon 64 FX 53, and all you are expected to know is that 53 is faster than 51.

There's no criticizing AMD for their Athlon 64 FX series numbers simply because it was our distaste with their original model numbers that brought this nomenclature about. We criticized the Athlon XP for using model numbers in the first place, we complained when AMD rated their processors to conservatively and then we lashed out at them for being too aggressive with the model numbers. Look at the facts, AMD labels the Athlon 64 FX as an "enthusiast" processor, only sends Athlon 64 FX parts out to reviewers - the fact of the matter is that AMD doesn't want to face criticism about their naming system any longer so they've removed it where possible, and kept it where they thought it was necessary. AMD will get no complaints from us about the series numbers attached to the Athlon 64 FX, it remains to be seen if the Athlon 64's model numbers will suffer the same fate as the Athlon XP's.

The FX goes back to using a ceramic package, as opposed to the organic packaging that the Athlon 64 uses. Both processors have an identical 193mm^2 die size (which is massive, these will be expensive chips to make) and are made up of 105.9 million transistors. The chips run at a 1.50V core voltage.

The 940-pin Athlon 64 FX will work in all 940-pin motherboards and the Athlon 64 FX 51 will be priced at $733 in 1,000 unit quantities.

AMD's Gem: Athlon 64 Socket-939: Athlon 64 FX DOA?
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  • Anonymous User - Tuesday, September 23, 2003 - link

    #10 Without XP64 only Linux apps can give great performance boost over 32 bits apps. Yes, I'm not a gamer, I don't care about UT2K3 or DX9 benchmarks.
  • Anonymous User - Tuesday, September 23, 2003 - link

    #19

    i agree. good review, and how anyone could see an AMD bias in that article, i have no idea. he fvcking said repeatedly that AMD isn't really cutting it with the A64/FX. the worst type of fanboy is one that cant read.

    its sad to see AMD lagging like this... if they fall too far behind, they wont be able to compete with Intel on a high-end level at all - which sucks for competition.
  • Anonymous User - Tuesday, September 23, 2003 - link

    That was a well written review.
  • Anonymous User - Tuesday, September 23, 2003 - link

    #15, doesn't the fact that you can buy an FX51 along with an Athlon64 3200+ at a variety of stores now contradict that statement? I mean someone even said they sighted them in retail stores and the sort across the world before even launch.
  • Anonymous User - Tuesday, September 23, 2003 - link

    For the non-fanboys out there, I have a couple questions.

    1. Is dual-channel really necessary for the Athlon 64? What is the bandwidth of the Hypertransport bus?

    2. Anand contends: "Ignoring the performance boost Intel gains by going to dual-channel, OEMs demanded a dual-channel solution from AMD simply as a checkbox feature." Do you buy this? I thought CPU manufacturers pushed the mobo guys around, not vice versa.

    3. After launching on two different Sockets (754 & 940) - is AMD going to convert everything over to 939 in '04, or are we going to see high-end on 940 and low-end on 754?

    4. Where are the UT2K3 64-bit version benches?

    5. I know it's kind of hard to judge, but how is the driver support for 64-bit coming along? (As a measure, does anyone know if nvidia and/or ATI will be ready with 64-bit drivers by the new WinXP64 launch?)

    6. This is more of a mobo/chipset questions, but where does PCI Express/3GIO fit into AMD's hypertransport plans?
  • Anonymous User - Tuesday, September 23, 2003 - link

    What i really dont understand is this: "AMD has lost a considerable amount of credibility" and again : "AMD has also priced the Athlon 64 and Athlon 64 FX very much like the Pentium 4s they compete with, which is a mistake for a company that has lost so much credibility"

    What exactly do you mean by that Anand?

  • Anonymous User - Tuesday, September 23, 2003 - link

    #13

    The FX-51 will not be avaiable in any reasonable quanitities until next year. The availability of any succeeding products is pure speculation.
  • Anonymous User - Tuesday, September 23, 2003 - link

    I think we'll see the athlon 64 outpacing the p4's in divx encoding once we see a 64bit enabled codec.
  • Anonymous User - Tuesday, September 23, 2003 - link

    All reviews (with exception of Toms Hardware and x86secret, go figure) show the FX51 outpacing the P4 Emergency Edition in the gross majority of benches. That's not even counting the fact the P4EE isn't even going to be available until November (making this a paper launch) and by it's availability the FX53 and Athlon64 3400+ will have already been out in the market with us looking forward to the FX55 in late 2003 or early 2004.
  • Anonymous User - Tuesday, September 23, 2003 - link

    #4 & #7. Please give me a couple of URLs (not thg) so i can validate your inspired response.

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