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Tested: DirectX 12's potential performance leap is insane

Gordon Mah Ung | March 27, 2015
We already know DirectX 12 will drastically improve game performance when Windows 10 ships later this year, but just how much of a "free" boost you'll get isn't exactly known.

Keep in mind that these are simulated performance results. The Core i7-4770K has 8MB of cache vs. the 2MB on a Celeron or 6MB on a Core i5 chip. I haven't found cache to make huge dents on most tests, and if anything my simulated CPUs would perform better than their actual counterparts thanks to the larger cache available. One other note: I had an issue underclocking the CPU to lower speeds while trying to simulate the Core i5-4670K. The lowest I could set it for was 3.6GHz, which is 200MHz higher than the stock part. 

No replacement for displacement

The takeaway from these simulated CPU tests is that thread-count trumps clock speed when it comes to DirectX 12 performance improvements.

Look at the results for the simulated dual-core Core i3-4330, which is a 3.5GHz CPU with no Turbo-Boost and Hyper-Threading. Compare that to Intel's low-cost wonder: the dual-core Pentium G3258 "overclocked" to 4.8GHz. Nicknamed the Pentium K by budget gamers, the chip is the only unlocked dual-core chip in Intel's lineup and cheaper than dirt. It overclocks easily, and just about anyone should be able to push a real one to 4.8GHz.

But look at the benchmark results: Despite running 1.3GHz higher than the simulated Core i3, the Pentium G3258 isn't much better in DX12 draw calls. This isn't anything new. In tests I've performed with CPUs as far back as the 2nd-gen "Sandy Bridge" Core processors in 2011, I've seen a 1GHz overclock on a Core i5 chip hit roughly the same performance as a stock Core i7 with Hyper-Threading in heavy multi-threading tests. 

DX12 also seems to scale nicely with core-count. Again, compare the dual-core, 4-thread "Core i3-4330" with the quad-core, 8-thread Core i7-4770K. It's almost exactly double.

Unfortunately, PCWorld's 8-core Core i7-5960X was working on another secret product so I didn't have time to test it with 3DMark's new feature test. I see nothing to make me believe that the test, at least, will scale nicely with an 8-core, Hyper-Threaded CPU.

The silicon elephant in the room is also AMD's FX series. Generally AMD CPUs are inferior to their Intel counterparts clock-for-clock. A quad-core Haswell CPU generally lumps up an "eight" core FX chip in the vast majority of performance tests. But that FX chip, though it uses shared cores, runs much closer to — and sometimes faster than — Haswell if the test is heavily multi-threaded. DirectX 12 may make AMD's often ignored FX parts hot again, since you can find an 8-core FX processor priced for as low as $153. 

At some point, I'll hopefully spool up an FX box to see if that advantage indeed crops up in DX12. 

 

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