AMD's 8 core Bulldozer FX chips review round up

Adam Oxford at

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AMD's FX series processors are finally released into the world today. Based on the company's brand new Bulldozer architecture, the first FX CPUs have between four and eight core designs, are sold with liquid cooling, and will cost from $119 to $245 (SRP).

Bulldozer is the first CPU that AMD has designed from the ground up since the Athlon 64 in 2003. If it feels like we've been waiting years for it, that's because we have. The processor launched today first appeared on AMD roadmaps back in 2007, and was originally scheduled to arrive in 2009. There's been much speculation about its potential performance and whether or not it's a viable competitor for Intel's Core series, which something AMD has been lacking for some time. Today's the big day that we finally find out.

The important thing is that the Bulldozer design will underpin future chips the AMD line-up for some time to come, just as the K8 design of the Athlon 64 was the basis of Phenom and Phenom II. A revision to Bulldozer which includes on-board graphics, called Trinity, has already been confirmed for next year, as have server versions of the chip with up to 20 cores.

Today, however, AMD is launching seven chips, ranging from the low cost, four core FX-4100 to the eight core flagship, the FX-8150. Behind the names, there's an unusual design, which requires a bit more explanation than the traditional CPU divided up into self contained 'cores'.

In the Bulldozer design, what AMD has done is to look at the way parts of a core are utilised and throw more silicon at the bits that need it. A basic Bulldozer building block, or module, has two separate integer cores but just one floating point core and a shared prefetch and decode unit. As a result, AMD counts each of these modules as two cores, so a four module chip is an eight core processor in AMD terminology. Technically, they aren't true dual core modules in the truest sense, but should perform like one in most circumstances - moreso than Intel's Hyperthreading, for example.

The top end FX-8150 processor is a four module, eight core chip with a base clockspeed of 3.6GHz. Just like Core CPUs and Phenoms, the FX base clockspeed is the one it rarely runs up. It has two automatic overclocking modes which allow the chip to run faster when required, provided that the maximum power draw isn't exceeded, and can shut down cores when not in use to save power. The first auto-overclocking mode is 'Turbo Core', which can speed up every core on the die for multithreaded opertations, the second is a more aggressive 'Max Turbo' which kicks in if less then half the cores are being utilised and allows for even higher speeds.

All FX processors have an unlocked multiplier to enable BIOS overclocking by the owner too, and AMD has also launched a revision to its Overdrive desktop software to tune the chips from within Windows.

One very useful thing about Bulldozer is that from a hardware perspective, it should drop into current generation 900 series motherboards as an easy upgrade for existing AMD-based PCs. It's also compatible with older motherboards that have an AM3 socket, if the manufacturer releases an appropriate BIOS update.

Does Bulldozer live to our expectations? What were our expectations? It may not come as a surprise to anyone who's followed the story of Bulldozer's development thus far, but it is disappointing to find out that AMD is pitching the first FX chips as superior to Intel's four core Core i5 range, but not as a competitor to the higher performing Core i7s which can handle 8-12 threads thanks to hyperthreading. According to the official blurb, AMD reckons it'll beat a top end Core i5 2500K in gaming benchmarks, although it falls short of Core i7 performance.

Still, says AMD, it's a lot cheaper than an i7 and in applications that make a lot of use of multithreading, like video encoding (without GOU acceleration) and photoediting, it's close to the performance of Intel's current six core chips.

I haven't had a chance to test Bulldozer fully just yet, so I'll reserve my judgement until I've been able to put it through it's paces. But what does the web think? Here's a round up of the best reviews so far, and unfortunately none of them make happy reading for AMD. I'll be adding our own as soon as we get hold of a sample chip to test.

Our sister site TechRadar says that the flagship FX-8150 is "inevitably... something of a disappointment". In games, especially, they find the FX-8150 lags behind the cheaper Core i5 2500K, and it's quite power hungry too.

Anandtech is also deflated. "The improvement over the previous generation Phenom II X6 simply isn't enough to justify an upgrade for existing AM3+ platform owners" says Mr Lal Shrimpi. Still, he optimistic about future processors based on Bulldozer.

Tomshardware concurs, saying that FX does well in multithreaded programs but doesn't have the overall performance to compete. "The processor falls on its face in apps that clearly weren’t written for the “go wide” approach to procuring performance", they say. Whatever that means.

The ever thorough X-Bit says "AMD didn’t succeed in launching a revolutionary desktop CPU".

And then there's.... well, you get the picture. There are scores of other reviews but they all couch their findings in the same language of disappointment. Which isn't just bad news for AMD, it's a problem for anyone who thinks competition is a good thing for innovation and price in the processor world.


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