Tue Mar 18, 2014 5:43 am
Intel's Haswell and Ivy Bridge cores are roughly 50% faster while running at significantly lower clocks than AMD's Piledriver cores (I say Piledriver since we're talking about 8-core models). So, to illustrate, let's say a single Piledriver core found in the FX-8350 which is running at 4.0GHz produces 8 billion results per second, and an Ivy Bridge core found in the Core i7-3770K and running at 3.5GHz can manage 12 billion results per second. Note that this is for illustrative purposes only and there's no way a particular core design will always perform similarly relative to another core design with all types of code mixes. If you use all the cores in each processor, the FX-8350 may actually beat the Core i7 if we assume that the app can really scale well across many cores and not just throw a few light threads at some of the cores or some other factor related to multi-threading is limiting performance (you might want to read up a bit on Amdahl's Law). If the apps you use can well utilize as many cores as there are available, going the FX route may be a sensible choice as long as you don't mind AMD's lower energy efficiency/higher power consumption. To make their FX chips more compelling, AMD prices them very competitively and boards for FX processors generally offer more value for money. If, however, your apps generally use only a few cores then obviously most of the cores in the 8-core AMD chips are just going to sit idle while the apps run on just a few cores which can only produce 8 billion results each (again, this figure is just our example to illustrate my point). In this case, you're better off with a Core i5 or, if you're willing to spend, a Core i7. Inversely, boards for Intel processors also tend to be more expensive than similarly specced boards for AMD FX processors.
Here's the theoretical math:
If you use all available cores,
Intel = 4 x 12 = 48 billion results
AMD = 8 x 8 = 64 billion results
If you use only 4 cores,
Intel = 4 x 12 = 48 billion results
AMD = 4 x 8 = 32 billion results
Let's say your app uses 7 cores,
Intel = 4 x 12 = 48 billion results
AMD = 7 x 8 = 56 billion results
As for the common belief that 8-core FX chips only have 4 FPUs, this is simply wrong. Each dual-core module in the FX contains two 128-bit floating point engines that are accessible to both cores and both can work independently of each other. However, both 128-bit FP engines can be ganged together to work on bigger chunks of data and this feature is available to both integer cores within a dual-core module. AMD calls this FlexFP. Obviously, if both FPUs are being used by a particular integer core, the other integer core within the module in question will have to wait its turn.
NEC V20 > AMD Am386DX-40 > AMD Am486DX2-66 > Intel Pentium-200 > Cyrix 6x86MX-PR233 > AMD K6-2/450 > AMD Athlon 800 > Intel Pentium 4 2.8C > AMD Athlon 64 X2 4800 > AMD Phenom II X3 720 > AMD FX-8350 > RYZEN?