The Jury is Out on AMD Quad FX Performance

Word on the official name of AMD's '4x4' double-dual-core platform, now 'Quad FX,' leaked out yesterday a day ahead of schedule. But even the first reviews of the new processor leave open some key questions.

Since last July, processor enthusiasts have been waiting for AMD to make its move, the response to Intel's Conroe (Core 2 Duo, Core 2 Extreme) that the company had promised. AMD's fans are looking for the Quad FX series - its new dual-socket computer platform - to even the score with Intel, and help the company recapture the price/performance crown it appeared to lose for the first time in several years.

From early indications from the most respected hardware enthusiasts' sites, including Tom's Hardware Guide and Anandtech, Quad FX may not eclipse Intel's recently-released quad-core Core 2 Quad series in performance just yet. But the announced prices for all three models in the Quad FX series are not extravagant, with pairs of 3.0 GHz FX-74 processors (Quad FXs will all be sold in pairs) going for a suggested retail price $999. FX-72 2.8 GHz CPU pairs sell for $799, and FX-70 2.6 GHz pairs sell for $599. Street prices, once the units officially go on sale, could be somewhat lower.

Still, while AMD's high-performance prices are indeed heading lower, they may still have a ways to go, judging from our initial calculations.

The first performance numbers we've seen put the FX-74 in contention not with Intel's top-of-the-line quad-core QX6700, but instead with Intel's more moderate dual-core Core 2 Duo E6700. A check of PriceWatch shows the E6700's average street price currently at $523.50. With AMD CPU street prices on the high end selling for 6% below the processor-in-a-box price, a $60 price break on the FX-74 won't go far enough.

Tom's Hardware Guide's Patrick Schmid suggested today that AMD enthusiasts could still consider the lower-priced FX-70 a bargain, if he's willing to overlook some critical facts. "If your ego can live with the FX-70 entry-level model," Schmid writes, "you will have to pay only a somewhat reasonable $599. Most likely you'll be able to overclock the CPUs to at least 2.8 GHz, likely even to 2.9 or 3.0 GHz, by increasing the base clock speed. If so, you'll get kick-butt performance for a very acceptable price, considering that Intel's Core 2 Extreme QX6700 is still at $999."

What distinguishes Quad FX from AMD's previous top-of-the-line FX dual-core processors (FX-62, FX-60) as individual units is that they were designed to co-operate in pairs. The bandwidth for the HyperTransport memory bus was increased, and the company's crossbar switching technology - introduced years ago in preparation for the dual-core era - is highly leveraged so that the processor cores can share resources almost as though they were sharing the same die.

As Schmid characterized AMD's strategy this morning, "If we cannot provide a real quad core now, let's go and build something bigger with what we have."

For AMD to pull off this minor miracle in time for the holidays, however, it had to have at least one working motherboard chipset under way. Of all the possible ironies, AMD -- the new parent company of graphics producer ATI -- had to rely on its existing partnership with ATI's sole rival nVidia, to pull off the launch before the end of November. NVidia's nForce 680a chipset has made it in time. ATI, you see, is not in the motherboard chipset business; and certainly, Intel wouldn't be a willing partner. Via Technologies and SiS remain, though neither has nVidia's current clout in the high-performance segment.

When Quad FX was first announced back in June (then code-named "4x4"), AMD characterized it as appealing to gamers and enthusiasts, picking up on the current target consumer for its FX series. The problem is, certain types of parallelism can appear to lead to a performance hit. Maybe the hit is caused by the hardware, and maybe it's by the software that's testing it.

Today, Anandtech's Anand Shimpi is willing to bet that it's the software, as he reported FX-72 performance in one Quake 4 gaming benchmark to be slightly bested by an AMD FX-62 dual-core processor running solo.

"Even though the latest version of the engine is multi-threaded, there's no real benefit above two cores," Shimpi noted today. "We will have to wait for the next-generation of titles before we'll start seeing real boosts in performance for quad core CPUs."

Perhaps one of the earliest sources to get to the heart of the matter is Wolfgang Gruener, who this morning reported in TG Daily that AMD is now characterizing its performance gains as mainly visible when you run multiple tasks as once ("task" here not always meaning "game").

"While Intel's Core 2 Extreme QX6700 can excel at almost any discipline," Gruener writes, "Quad FX systems aren't quite gaming systems, but rather multitasking, or as AMD calls it, 'megatasking,' machines. Translation: The more applications you throw at it at the same time, the more you can see the system's capabilities. For example, AMD claims that a Quad FX system can run demanding games as well as HD video encode and decode at the same time."

That kind of "megatasking" could very well end up being the kind of work an enthusiast might do, maybe if just to show off. The problem for AMD is, how many of these show-offs are out there, and do they constitute a sizable enough purchasing segment?

If somehow, all things really are being equal (which they never are), Quad FX and Core 2 Quad performance were even, and prices were on the level, then one factor which could still tip the scale is the power envelope. AMD has long been the low voltage leader, to the extent that its championing of low power was perhaps the sole catalyst breaking Intel free from its power-hungry NetBurst architecture.

But each die in a Quad FX pair is being rated with a thermal design power (TDP) envelope of 125 watts (AMD will argue that's assuming the maximum power envelope and not the mean wattage, which may be lower). Double that -- which you must -- and the TDP maximum becomes a fearsome 250 watts.

Even if you take AMD at its word that Intel cites mean wattage as TDP, its own 125-watt figure for its Kentsfield architecture Core 2 Quad could yield a maximum of something toward, though probably less than, 250 watts. So while AMD tries to regain an advantage in one category, it may be ceding the advantage in another.

If there's an undeniable immediate benefit to be found for AMD, it's in the fact that its announced Quad FX prices are driving street prices for its existing processors down. Athlon 64 FX-62 prices have fallen 21.7% since their average at the beginning of this month, to $669.50; and Athlon 64 X2 5000+ prices have subsided 24.8% in early November, to $325.63. Intel multicore prices have fallen about 15% on average during the same period.