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.

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

    #38, Huh how heck are we forgetting something NO ONE KNOWS? Has Intel ever really givin an absolute upper limit to the Prescott clocks throughout the year? Last time I heard Tejas would takeover after 4.2Ghz.
  • Anonymous User - Tuesday, September 23, 2003 - link

    LOL, you all who think that intel is the winner here, just continue to believe so, but don't tell anyone.

    If Prescott was so great we should have seen "leaked" benchmarks by now. I saw benchmarks of the Clawhammer more than a year ago.

    AMD can not outperform intel because they'll get problems with their supply. That's one of the main reasons AMD don't want to release a cpu that will beat all intel offerings. Imagine what will happen if everyone wants an AMD.
  • Anonymous User - Tuesday, September 23, 2003 - link

    #35, Dude just frigging be quiet as I seriously hope you aren't saying crap like that in public.
  • Anonymous User - Tuesday, September 23, 2003 - link

    You guys are forgetting Prescott is capable of 4.6 GHz, and it'll have the price advantage.
  • Anonymous User - Tuesday, September 23, 2003 - link

    So what's the difference between 32bit with 64bit extensions, and 64bit with 32bit compatible mode.

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

    #29, Didn't Intel reps at IDF make comments to the tune of a 3.2Ghz P4EE offering up better overall performance than a 3.2Ghz Prescott? How heck is Prescott going to change things when it's debutting at 3.4Ghz and going to be up against an FX51 and A64 3400+ (possibly even FX55)?!!?? What part of that shows Intel sailing through 2004 when Prescott is expected to max out at around 4Ghz and A64 hasn't even gone through a die shrink and is already performance competitive with it from the initial 130nm A64 releases??!?
  • Anonymous User - Tuesday, September 23, 2003 - link

    Athlon64 isnt running in 32bit compatibility mode. It's still a 32-bit processor with 64-bit extensions, not the other way around. Pure 64-bit processors will trounce it in 64-bit apps.

    Just keeping up with Intel isn't enough, they needed to take the performance crown without any doubt to really gain back marketshare, right now this is just good enough to tread water, especially considering their pricing. How the next year plays out will be interesting though.
  • Anonymous User - Tuesday, September 23, 2003 - link

    #32

    Wait till next year when the bugs of 64-bit drivers/software come onto your system. It will be Windows 95 all over again. AMD64 is an expensive disappointment.

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

    amiga owns you.
  • Anonymous User - Tuesday, September 23, 2003 - link

    For everyone saying that the Athlon64 was NOT the so-called AMD Killer, I just have one question:

    How can you say a 64-bit processor running in 32-bit compatibility mode that keeps up with the best Intel processor, the P4EE, disappointing? Me, I'm waiting for some more 64-bit programs to judge the strength of the Athlon 64. The fact that the Athlon 64 can keep up and sometime pass Intel in 32 bits is awesome.

    BTW, I'm not an AMD fanboy. I have both AMD and Intel processors. But I find the Intel zealots are trying to discredit this processor by insisting on only looking at half the picture. Just my opinion.

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