Bulldozer Final Thoughts

Those of us hoping that AMD's Bulldozer CPUs would catapult ahead of Sandy Bridge performance must live with the disappointment. Considered on its own, the AMD FX-8150 CPU is a great processor with excellent performance (especially if you can keep all eight cores busy), and in many cases beats the Intel Core i5 2500K. But there are few real-world applications that gamers and enthusiasts use that will fully exploit it; in fact, as you can see from many of these benchmarks, even programs designed to spawn multiple threads frequently do not scale their performance well past four cores.

Of course, having eight cores also means you can have a lot of background stuff going on and still keep things perky in the foreground application, and AMD has some persuasive demo videos showing how much smoother multitasking is with real cores as opposed to virtual cores, but it's a hard thing to quantify.

The 32nm fabrication process and other architecture improvements give the FX-8150 good overclocking headroom, and AMD's aggressive turbo frequencies represent the first officially-supported 4GHz and higher clock speed in any consumer CPU. But the Core i5 2500K has lots of overclocking headroom, too. Since overclocking results aren't guaranteed, the comparison chart below is based on each CPU's scores at stock clock speeds.

Using these benchmarks, the stock-clocked AMD FX-8150 averages 2.2% slower than the stock-clocked Intel Core i5 2500K. But as you can see looking at this chart, the individual differences are typically much higher: the FX-8150 tends to win big or lose big. It would be easy to choose a mix of benchmarks that gave a decisive win to either CPU, but I tried to use as broad an array of tests as I could to give the most accurate performance comparison.

As I showed in the single-core section, the performance of a Bulldozer core is not significantly better than the performance of the older AMD Thuban core, and both are far behind a Sandy Bridge core, so AMD's banking on keeping all eight cores filled to get the best performance. And indeed the FX-8150 can return excellent performance in these cases, although the performance improvement is less than what you might expect given the extra cores. And if software vendors upgrade their products to use the new instructions AMD has integrated into Bulldozer, its performance will improve more.

AMD claims the Windows 7 thread scheduler doesn't make the best use of Bulldozer's architecture, and says that we can expect a 10-15% performance improvement when Windows 8 ships. Also, Bulldozer is just the first in a line of new processors: in the coming years we'll see Piledriver (2012), Steamroller (2013) and Excavator (2014), each of which AMD says will bring improvements in performance-per-watt and instructions-per-clock.

But Intel's not standing still. Before the end of the year we should see Sandy Bridge "E" processors, and next year we'll see the 22nm Ivy Bridge processors, which according to rumor will drop right into existing Cougar Point motherboards, enabling Intel users to easily upgrade their systems. AMD FX CPUs are only officially supported on AMD 9-series chipsets, although several vendors have said that their 8-series motherboards will support FX processors with a BIOS upgrade. When specifcally asked about this, AMD said only that official support is limited to the 9-series chipsets, but that individual vendors were free to do what they wanted. We'll see, I suppose.

Given the market for this processor, you might wonder why I didn't include game benchmarks. The reason is simple: at high resolutions (say 1080p and above) and with multi-monitor systems, the critical factor is your video card setup, not the processor. Assuming the same video card configuration, your Bulldozer gaming rig will not give you a noticeably different experience than your Sandy Bridge gaming rig. If you're an AMD fanboy like me, rest assured that a Bulldozer system is an excellent base on which to build a high end gaming rig.

A few weeks ago I attended an all-day press briefing on the Bulldozer architecture at AMD's Austin, Texas headquarters. One of the points AMD made was that performance is only one aspect of a processor; another is performance per watt. But while AMD's server processors and E- and A-series APUs excel in this area, the FX-8150's 125 watt TDP is 32% greater than the Core i5 2500K's 95 watts. Granted, most desktop system users don't consider processor power draw when designing a system, but there it is.

AMD's weakness remains its integer core (APU) performance, which Bulldozer does not significantly improve over Thuban. More cores can compensate for this in some circumstances, but overall in my tests the FX-8150 can be considered at best to have achieved performance parity with Intel's 2500K...at a $254 MSRP as compared to the 2500K's $216 MSRP.

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