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AMD Athlon 64 FX74 review

The quad core conundrum remains

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Our Verdict

An interesting sideshow for the multicore main event, but Intel still holds the centre stage

For

  • Competitor for Kentsfield

Against

  • Slower than Q6600

    Power hungry

    Noisy and expensive

Despite the fact that Intel's four core Kentsfield processors have been out for a few months now, we're still at the very early stages of the quad core revolution. Supreme Commander will be the first game on the shelves that can make use of four separate CPU cores at once for a performance boost, with Half-Life 2: Episode 2 to follow later in the year.

AMD's marketing department has coined the phrase 'megatasking' to describe running several CPU intensive tasks simultaneously - high def video encoding, gaming and MP3 streaming to an extender, for example. Getting PC owners to actually try running all that stuff on a regular basis, let alone feeling compelled to splash out on hardware that lets them do it, is going to take bit longer than it did to come up with the name, though.

All of which explains why Intel's Core 2 Extreme X6800 still costs system builders the same amount as a QX6700 quad core chip. It's slightly faster in games and single threaded applications, despite only boasting two cores.

Caveat over

If you were to ask us what chip to buy for tomorrow, though, we'd absolutely encourage you to go quad core. It's a technology that will really come into its own in the next few months, as more games appear that support it and Vista takes over from XP with its more efficient handling of multiple CPUs.

In professional applications - for audio, video, photo and 3D editing, for example - multi- threading is already the norm and as we found in our Kenstfield reviews, performance in optimised applications scales very nicely as you add more processors. Which is why we've been looking forward to AMD's response to Core 2 Quad quite keenly.

And here it is. Quad FX. Formerly known as 4x4, it's as different to Intel's solution as it's possible to be. First of all, where Intel's Core 2 chips are a brand new design from the ground up, Quad FX is simply two old-style dual core Athlons plugged into one board.

One of the key strengths of the AMD's 64-bit architecture, that enabled it to compete so effectively against Intel's Xeon server chips, is its ability to talk chip-to-chip and share memory resources across the Hypertransport bus.

The Quad FX compatible chips, which are designated FX 7x, use the new Socket F, which has a few more pins than its predecessor to enable this 'Direct Connect' communication between the processors. It's also AMD's first Landed Grid Array (LGA) design, which simply means the pins are on the motherboard, not the CPU - as previously introduced by Intel Pentium and Core CPUs.

Thanks to AMD's integrated memory controller, each chip has its own bank of memory divided into two slots. Each bank is accessible by the other chip over that Hypertransport link, but obviously at a slight penalty in performance. This is both the saving grace and, simultaneously, greatest failing of Quad FX as a platform, in our opinion.

Kentsfield's rival

On the one hand, the independent integrated memory controller and its bandwidth of 12.6GB/s per chip means that even with all four cores under load and making calls to the RAM, there's little chance of any bottlenecking - a potential risk for Intel's single chip, external memory controller which is dependent on the FSB once all four cores are screaming for data.

The problem at the moment for AMD is that this potential bottleneck isn't exactly holding Core 2 Quad as a platform back just yet. To make things worse, it means that each CPU needs its own RAM.

So the whole system needs 4GB, for example, to match a Core 2 Quad running on 2GB (its performance potential) which is going to be expensive when you consider this is a high end option that needs fast, low latency RAM to make the most of.

A further blow comes from the physical layout of the RAM - at least on the Asus board we reviewed with, which at the time of writing is the only Quad FX compatible board out there. All four slots - two per chip - are sandwiched between the processors, leaving no room for larger, quieter air coolers.

If only that were the least of our logistical problems, though. The two processors draw 125W a piece, which means that on top of the cost of the extra RAM and a very expensive motherboard, you're looking at a seriously meaty power supply too.

The sad thing is that historically, AMD had the no-brainer chip of choice over Intel because its processors were smaller, more efficient, cooler, more advanced and cost less for the same power - a situation that Quad FX has flipped completely on its head for the time being. In terms of our benchmark scores, not only is AMD's flagship FX74 setup more expensive than Intel's top-of-the- range QX6700 (£700 versus £627 at last count), it's outperformed by the £550 Q6700.

Quad FX, as a processor platform for the future, may yet come of age. There's an Athlon revision later in the year that will put AMD on a steadier footing against the Core micro-architecture, and that very clever memory handling may come into its own with Vista and 'megatasking'. But right now it remains a curio, it looks like a knee jerk counter to Kentsfield and it certainly isn't deserving of your hard-earned cash.