[rockaway]

A major question for some people getting ready to buy a high-end system is whether they want or need to have two processors available to them. For anyone doing video editing, multi-threaded applications, or a lot of multitasking the answer is a very clear 'yes'. Then the question becomes whether two separate processors (as in a dual Xeon or Opteron system) is the way to go, or whether a single dual core processor (like a Pentium D or thlon64 X2) will do just as well. Dual CPU vs dual core -- which is better?!


Intel did not increase the speed of their front-side-bus (the connection between the CPU and the motherboard) when they switched to dual-core, meaning that though the processing power doubled, the amount of bandwidth for each core did not. This puts a bit of a strain on the Intel design, and likely prevents it from being as powerful as it could be. To counteract this effect, Intel continues to use faster system memory to keep information supplied to the processor cores.

AMD, on the other hand, does not use a front-side-bus in the traditional sense. They use a technology called HyperTransport to communicate with the chipset and system memory, and they have also moved the memory controller from the chipset to the CPU. By having the memory controller directly on the processor, AMD has given their platform a large advantage, especially with the move to dual-core. The latest generation of AMD single-core processors can use single- or dual-channel PC3200 memory, but it is interesting to note that even though dual-channel operation doubles the memory speed, it does not double the actual memory performance for single-core processors.

[carlosponti]

I will state right off the bat being that i have ran dual processor systems. Most of the time Software isn't even written to handle two processors even if the operating system is able to handle it. dual core i am not sure how that works with OS and support software.

[valan]

I don't know for sure that one is better than the other. Dual processors is more expensive for sure, you need a special motherboard and 2 processors, where dual core uses just the standard motherboard with today's standard processors. The software sees two seperate processors on a dual core machine just as it sees 2 seperate processors on a dual processor machine, too. The advantage is when you start moving up to more cores. A quad core cpu is still just one cpu, even though the software sees 4. It takes a huge and expensive setup to match that with four single core processors.

[bigtomrodney]

Multi core CPUs are still multiple CPUs, it's not an illusion. The hyperthreading technology of a few years ago was a way of fooling the PC. From personal experience I can say that running a dual core vs. two CPUs, the dual core wins out. Remember that multiple CPU systems are quite inefficient in that they communicate over the slower system bus.

In the case of Intel Quad cores they are actually two sets of dual core CPUs as they had not yet perfected communication between four cores.

[techieMoe]

From a practical, monetary standpoint you're better off with a dual-core single processor. Xeon and Opteron chips require special motherboards and usually fully-buffered RAM, which costs a pretty penny more than standard PC components.

[genesus]

Originally Posted by bigtomrodney

Multi core CPUs are still multiple CPUs, it's not an illusion. The hyperthreading technology of a few years ago was a way of fooling the PC. From personal experience I can say that running a dual core vs. two CPUs, the dual core wins out. Remember that multiple CPU systems are quite inefficient in that they communicate over the slower system bus.

In the case of Intel Quad cores they are actually two sets of dual core CPUs as they had not yet perfected communication between four cores.

Thanks BigTom, I'd always assumed, and you know what they say about that, that dual processors would be quicker. I can keep my opteron an use my meager upgrade budget on more necessary parts

I thought that the dual-cores used hyperthreading technology.

[bigtomrodney]

Originally Posted by genesus

Thanks BigTom, I'd always assumed, and you know what they say about that, that dual processors would be quicker.

The way I see it they're much the same. Both are significantly better than a single CPU but neither double performance. I kind of just view dual core vs. dual CPU as being another step in size reduction albeit with slight variations.

I thought that the dual-cores used hyperthreading technology.

They may well do too, but the Pentium 4 generation hyper threaders were a big marketing scam in my book. All they did was swap processes and simulate a two CPUs. I know AMD use Hyper Transport though.