Cores in CPU

Ok seems I have been misinformed by some on the internet. I always thought dual core, core 2 duo and quad core were 2 and 4 processors. Literally 2 and 4 processors in one computer. Do cores mean processors or something else? I was corrected recently(by a rude, nonetheless, microsoft store employee) that cores mean pathways to a single processor. Can someone clarify what dual and quad core mean? thx

 

Core 2 Duo is a processor brand, coming in dual- and quad-core models.

For Intel processors, you can easily determine how many cores it has by searching the CPU model in Intel's database. In laptops, *any* CPU that has -QM at the end of the model name (such as i7-2720QM) is a quad-core, whereas any other Intel mobile CPU will be dual-core (-M, -U, etc).

AMD's A4 and A6 models are dual-core, and their A8 and A10 models are quad-core. This is going by the integer core count, but every pair of integer cores shares a floating point unit (whereas each integer core in Intel CPUs has its own FPU).

 

Your right, they are. At one time they were discrete or separate.

Today each core or processor are placed on one chip for speed and efficiency.

Multi-core processor - Wikipedia, the free encyclopedia

 

EDIT: Didn't see the post by hydra when I wrote this post.

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Wiki can explain it well:

http://en.wikipedia.org/wiki/Multi-core_processor

Here is what a quad core i7 cpu looks like. You can see there are 4 cores on a single processor.
So core 2 duo and quad core have 2 and 4 cores. But those cores are parts of a single processor.

 

Nice picture and everything that needed to be said has been said. Aside that certain versions of windows will support multi core CPUs, but not support multiple CPUs while other versions support both. Another difference is that the cores on a CPU share some of the resources available on the CPU such as the L3 cache while separate CPUs would each have their own cache instead of sharing the same.

Essentially, as other members have said, a quad core CPU is pretty much 4 CPUs in one chip.

 

Very nice, moral hazard.

If I remember correctly, earlier architecture quad cores (such as Core 2 Duo quad core CPUs) had two cores, and then a core within each core. Don't quote me on this; I'm reiterating info another technician told me years ago. But basically, each core within a processor is able to carry out a pipeline - or set of instructions - thus improving multi-tasking performance and allowing for background processes to not slow down the system.

Multi Core CPU:



Multiple Processors (side-by-side sockets):

 

I look at it this way, imagine a bank. Some small banks only have a single teller with a single line due to small premises. This single bank building is the Processor with a single bank teller (Core). A much larger bank with bigger premises might have 2 or 4 tellers (dual and quadcores) but still only one building (processor).

The confusion is because the definition of processor has changed. CPUs used to have only a single set of decode, fetch, thread dispatch, execution and cache elements (i.e. a Core) which allowed it to do its job, in this case, processor was synonomous with core. Eventually with Core 2 Duo, most elements within the processor got duplicated so it became a dual-core (i.e. 2 processing cores) which comprise a single processor.

The Core 2 Quad was simply 2 Core 2 duo dies networked together on a single package hence a quadcore processor. Nehalem was a true quadcore in the sense that there quadplicated elements but also stuff like the L3 cache which was shared between the cores. So basically, the Core 2 Quad bank has 2 separate rooms, each room has 2 tellers with their own Cash and check facillities, each serving a single line of customers, the two rooms can only communicate with each other via 4 really fast messengers. Whereas the Nehalem bank has 4 tellers in a single room so no need for inefficient messengers.

To add to the confusion, there is hyperthreading which very simplistically is a method to allow 2 threads (or instruction streams) to be simultaneously processed by a single core thus improving utilization of said core. This means that a Nehalem (i7) processor will present to Windows with 8 cores but with only 4 physical cores. In the banking analogy, hyperthreading basically means that the Nehalem bank has 4 tellers, each with their own cash safes and check scanners/dispensers but each teller is tasked with serving 2 lines of customers simultaneously.

Things get really confusing with AMD's Bulldozer/Piledriver (AMD trinity). I alluded to earlier that a Core has fetch, decode, execution and writeback elements. AMD basically only duplicated about 3/4s of a core and what isn't duplicated got increased in power. Simplistically, AMD duplicated the Integer execution engine so a full module has 2 integer cores (the parts which allow Addition and Subtraction of numbers) but only 1 albeit really powerful Floating Point unit (the part which allows Multiplication and Division). There were some other shared elements as well. AMD basically networks several of these "modules" in to a Processor. So depending on your definition of core, a full AMD Bulldozer Processor is an 8 core (if you count integer only) or a quadcore (if you count cores as having Integer and Floating point units). In the Bank analogy, the Bulldozer bank has 8 tellers with a single line each, because management is really stingy, 2 tellers have their own cash facilities but must share a single fast scanner for depositing or dispensing checks. So the Bulldozer bank acts like an 8 core CPU if the customers only want to deposit or withdraw cash but it acts like a Quad core if customers only want to deposit/sign out checks. The reality is there are a mix of customers wanting to deposit cash/checks or even the same customer with multiple transactions similar to computer code so the Bulldozer bank is never quite a true 8 core but never quite a true quadcore.

I hope this helps