@NoelC and @Mcinwwl yes and no: AMD Bulldozer's architecture uses Clustered Multithreading and has these things called "clusters" which it uses to process stuff. These clusters have two integer (aka ALU) units, one floating point unit (aka FPU), and share an execution engine (aka EX, the "do stuff" part). This basically makes the "cluster" (aka "core") equivalent to a dual-core processor in integer math, and a single-core processor in floating-point math. Now, having double the APUs is great for heavily multithreaded applications and there is a measurable advantage in certain types of applications. Anyway, the Bulldozer "clusters" share FPUs and L2 caches, and this causes single-threads to process slower since they have to "wait" for shared resources (aka serial, or in-order, processing). Hence, Bulldozer "clusters" have slower single-threaded performance as they get stuck in the queue. The Nehalem (Intel) architecture and its children use Symmetric Multithreading, which uses two identical logical processors per "core" - similar to an AMD "cluster," but with 100% of the same resources available to both processors. Each "core" has the equivalent of dual-core APU and dual-core FPU resources, and also shares an execution engine. But, since the processors in the "core" do not share resources in the same way as Bulldozer, it doesn't get stuck waiting for stuff to do. Let's suppose you have an 8 core/cluster AMD and a 4 core/8thread Intel. Your operating system really only sees 8 logical processors when it has to assign threads, so it assigns 1 per cluster, even though the cluster can really do two threads (if they're integer math). When things get stuck, this pretty much makes each "cluster" half the FPU performance of an equivalent Intel "core" and reduces the ALU performance advantage. Intel is faster per "core" in single-thread performance than AMD "clusters" due to their architectural differences. Additionally, Intel's improvements to their execution engines and resource scheduling have caused their 4 "core" (8 thread) processors to eliminate the advantage of 8 "cluster" processors in multi-threaded performance. Fortunately, AMD is abandoning clustered multi-threading in favour of simultaneous multi-threading (like HyperThreading on Intel). In other words, AMD processors have to "wait a lot" for shared resources in single-threaded applications, Intel processors don't, and even though threads are assigned by the OS, the threads a CPU shows to the OS and the way it shares resources across cores are a key point for single thread application. That's pretty much it and sorry for the wall of text.