AMD preparing Athlon 64 FX?

But is it a low-end part or a DP chip?

AMD's Athlon 64 - already the source of much speculation over the number of pins each packaged chip will features, 754, 939 and/or 940 - has become embroiled in rumours centring on the company's FX nomenclature.

AMD will launch the Athlon 64 on 23 September, that much is known. But German web site Planet 3DNow is claiming it will ship a chip called the Athlon 64 FX alongside the regular Athlon 64.

The site reckons the FX chip is the 940-pin Athlon 64, while the standard Athlon 64 will sport 754 pins. Both parts will operate at 2GHz, with the 754-pin part branded the Athlon 64 3200+ and the other one the Athlon 64 FX-51. The former supports a single-channel DDR SDRAM bus, while the FX can handle a dual-channel bus.

The logical assumption is that the FX part is actually an Opteron. This makes some sense. Earlier hints about the Athlon 64 pointed to two versions, one for single-CPU systems, the other for dual-processor rigs. The Athlon FX may well be the latter, and AMD is simply re-branding Opterons accordingly.

But Opteron yields are not supposed to be too good right now, so how can AMD produce enough to satisfy Opteron and Athlon 64 demand? We recall seeing early dual-processor Athlon 64 specs which pegged the part at 512KB of L2 cache. A piece over at Adrian's Rojak Pot reckons that Opteron yields are down because the cache is failing in some dies. The Opteron L2 cache takes up more than 50 per cent of the die area, so that's entirely plausible. The site suggests that AMD is testing failed 1MB to see if they can support 512KB of L2.

Obviously, it can't sell such processors as Opterons, but it can offer them as low-cache Athlon 64 DPs - or FXs, if the Planet 3DNow report is correct. They'd only have to be thrown away otherwise.

Planet 3DNow speculates that the Athlon 64 FXs will be offered as low-end Athlon 64s rather than dual-processor models. Rumours that emerged in July that AMD was working on a low-cost 32-bit chip called the Athlon FX, based on the Thorton core, as a replacement for the Duron, would suggest the Athlon 64 FX is a low-end part.

At the time of the Athlon FX rumours, our AMD sources told us the 'FX' naming scheme had nothing to do with Thorton, and in any case was only a suggestion for possible product branding.

If Planet 3DNow's information is correct, it looks like that the company has indeed decided to use the FX tag. However, whether it's for a low-end part remains to be seen - yes, the FX has a lower cache than a regular Athlon 64, but what about the dual-channel memory support? That surely suggests a higher end chip, which is why we reckon it might just be the dual-processor version once talked of.

Either option offers a difficult choice for AMD. If it's a dual-processor chip, it could cannibalise Opteron sales, and if it's a low-end part, it could limit both Athlon 64 and Athlon XP sales. Then again, the economics of utilising Opteron chips that are landfill otherwise may make sense in the setting of the grand AMD Excel spreadsheet. ®

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