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CPU Cores

by Parm Mann on 20 October 2008, 00:00


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Single and Dual Core Processors

Over the course of the last year or so we've seen GHz become less of a focus when it comes to processors. Instead, we're seeing a shift towards processors that do more work per clock, have larger caches, are more power efficient, and of course we've seen dual-core processors hit the market. So what is dual-core all about, and how does it weigh up compared to single-core?

How do they do it?

First, let's be clear on what a dual-core processor is. Dual- and multi-core CPUs have in fact been around for a while, but no on x86 hardware, so dual-core is new to this part of the market, but not new in a complete sense. When you're dealing with a dual-core processor, you have one processor package, and on it there are two execution units. So, you take one dual-core processor, drop it into your compatible motherboard, and as far as your Operating System is concerned, you have a dual CPU system.

The way in which dual-core is actually implemented can be different as well. You can combine two cores into a single die (the small, raised section on the CPU package, which you cannot see if there is a metal head spreader on your CPU,) or you can put two dies on the same package. Similarly, you can have a dual-core CPU where each core has its own L2 cache, or you might have a design where the L2 cache is shared between the two cores. There are technical and performance merits and drawbacks to these different methods, which we won't delve into in this article.

So, to sum up dual-cores, you've basically got two processing units on the same package.

An easy upgrade?

Now, those of you with the heart of an upgrader will have immediately thought about replacing your current single-core processor with a dual-core equivalent. Can it be done? Yes and no.

In the AMD camp, a lot of servers using socket 940 and desktops with socket 939 motherboards will be upgradeable with little more than a BIOS upgrade and a new dual-core CPU. There are some exceptions to this rule, but if you have a recent socket 939 motherboard, it shouldn't be hard to check whether you can upgrade to dual-core should you want.

If we wander away from AMD and into the Intel camp, it's a different story. If you've got an LGA775 based board, don't immediately assume that your motherboard has dual-core support. You'll need an i955 or i945 chipset for dual-core capabilities.

Where's the benefit?

Time for the big question. In a face-off between dual- and single-core processors, which is better? Right now, in terms of clock speed, single-core processors have the edge. But if you've got two cores at your disposal, won't that claw back a performance lead? It depends on what you're doing.

Right now, it's hard to find an application that will use two cores simultaneously. There are some out there, but the majority of programs will tie themselves down to a single processor. This includes games. So, in terms of gaming performance, you'll only get the use of one core. However, let us not forget that we're left with a second core doing nothing. So, if you've always fancied encoding your DVD collection to hard disk, you can do it while you're playing a game and in theory not notice a performance drop. You could also argue that the benefit of dual cores means that anything running in the background while you're playing a game (virus scanner, firewall, other utilities...) won't have as big an impact on game performance.

Change the angle from gaming to multitasking. If you have various applications crunching away throughout the day, you'll find they're more responsive with dual-core compared to single-core. Similarly, the multimedia maniac is likely to benefit from dual-core more than the gamer.

In a year or so, when more programmers and subsequently more applications embrace parallelism, we'll see single applications benefiting from dual-core processors. Until then, gamers should probably stick to a speedy single-core chip.

Further into the future...

Dual-core is just the beginning. Sony's Cell chip, which sits at the heart of the up-coming PS3, has eight cores. We'll see multi-core processors surfacing for desktop PCs at the end of 2006 and into 2007, bringing yet more performance and power consumption benefits.

In the meantime, sit back and enjoy the ride, as the world begins to embrace the world of dual-core.

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