AMD FX “Bulldozer” review

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It took AMD a long time to bring it to market, but Bulldozer is finally here to offer Intel’s all-conquering Sandy Bridge chips some much-needed competition. That’s AMD’s intention, anyway.

Bulldozer is henceforth to be known as AMD FX: the new range consists of four chips, from the £95 FX-4100 to the high-end, £195 FX-8150, and they share a brand new 32nm, socket AM3+ architecture.


AMD’s headline innovation is what it calls “Bulldozer Modules” – processor cores containing two physical execution units, and hence able to service two threads simultaneously. Each module features only a single shared pipeline, and a single floating-point arithmetic unit, so it’s not a fully dual-core design – but it should still deliver greater parallel throughput than one of Intel’s Hyper-Threading cores, which offer only a single execution unit.

In practice, it means AMD’s top-end FX-8150, with four modules, can process eight threads at once, bringing it into line with the best Intel chips. The cheaper FX-6100 has three modules serving six threads, and the FX-4100 has two modules to process four threads.

On the top-end CPUs you get 2MB of L2 cache per module, shared between execution units, and each unit has its own L1 cache, scheduler and memory bandwidth. 8MB of L3 cache is shared across the whole chip.


AMD claims its new architecture allows each core to be more efficient at multitasking, and it’s loaded the FX chips with a host of other improved features too. Turbo Core has been given a shot in the arm: last year’s models could only overclock half of their cores, but now every core in an FX chip is capable of boosting by up to 300MHz.

That’s less additional juice than before, but spread across more cores, which makes sense given AMD’s focus on multi-threaded performance. Turbo Core also now includes a Max Turbo mode which boosts the clock further, but only across half a chip’s cores: the FX-8150, for instance, will now be able to run four of its 3.6GHz cores at a tasty 4.2GHz.

Performance graph

That’s a bigger boost than you’ll see from Intel, which uses Turbo Boost to overclock its Core i5-2500K from 3.3GHz to 3.7GHz, and its i7-2600K from 3.4GHz to 3.8GHz.

Every chip in the new AMD range is unlocked for easy overclocking, and they’re all set up to handle dual-channel DDR3 memory running at up to 1,866MHz – an improvement over the 1,333MHz the old Phenom II could handle. Here, FX outstrips Sandy Bridge again, with the latter only officially handling up to 1,600MHz memory.

Top-end power requirements stay the same, with the most demanding chips possessing a TDP of 125W. AMD has introduced a new socket for its new CPUs, dubbed AM3+, but you might not need to upgrade: AMD’s FX chips are backwards-compatible with older AM3 boards with a BIOS update. Which motherboard manufacturers actually provide these, however, remains to be seen.

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