Mil/Aero Insider: February 2009

Multicore processors: more bang for the buck

It seems like a long time ago that the only thing anyone cared about in measuring processor performance was clock speed. Back in 1993, it appeared that the 66MHz offered by Intel’s new Pentium processor was all the performance anyone could need.

For all practical purposes, however, there is a limit to the speed at which a commercial processor can operate – somewhere under the 4GHz mark. To obtain further performance gains, processor manufacturers have increasingly started to look beyond raw speed, and have instead focused on the other factors that influence throughput, such as cache memory and front side bus speed. Beyond this, the latest generation of processors from Intel, for example, feature 64-bit processing rather than 32-bit.

What has captured most people’s imagination, however, has been the advent of multi-core processors – in effect, single blocks of silicon that contain more than one processor. One of the advantages of this approach is, of course, that less board real estate is consumed than if two separate single core processor chips were implemented, allowing for the continuing trend to increase on-board functionality.

It could be assumed that a dual core processor will deliver twice the throughput of a single core processor, given identical processor clock speeds. Inevitably, this is not entirely the case. For multi-core processors to deliver on their potential, the environment in which they are deployed must be appropriate. What does that mean? It means that the number of separate tasks that require access to the processor must be at least equal to the number of processors. For a desktop PC environment, for example, more than one application program needs to be running concurrently – Word and Excel, for example. A single application will not run twice as fast on a dual core processor.

That, though, is not the whole story. For multicore processors to deliver tangible benefit, the operating system needs to know how to leverage them to best effect. Tests have shown that, for example, while Windows XP is able to take some advantage of multicore processors – it inherited a symmetrical multiprocessing capability from Windows NT – newer operating systems like Windows Vista and Windows 7 have been designed specifically with multicore processor hardware platforms in mind, and are able to take much more advantage of the multicore architecture.

In a real-time environment, the same needs to be true. When LynuxWorks, for example, announced LynxOS 5, the headline news was that it provided support for multicore hardware. Green Hills Software’s INTEGRITY 10 and Wind River’s VxWorks similarly provide multicore support.

In a scientific application, the requirement may be that a single task lends itself readily to a high degree of parallelism – and will ideally be an application that is CPU-intensive rather than, for example, I/O-intensive: with appropriate software design – and operating system support - multiple calculations can take place in parallel, rather than sequentially.

Today, the best known example of a multicore processor is probably Intel’s Core2 Duo. Announced in 2006, it has already seen several iterations, each with increased clock speed: Core2 Duo processors announced in January this year, for example, feature clock speeds of 2.8GHz. However, of at least as much interest to military customers is the heat dissipation of processors. GE Fanuc’s recently announced Core2 Duo T9400-based V7875 single board computer is rated at 2.5GHz – but the power dissipation of the T9400 is only 35 watts. This performance/power ratio compares vary favourably with, for example, the 65 watt – 130 watt dissipation of many other members of the Core2 Duo family.

In the military market, the primary competitor for Intel’s multicore offering comes from Freescale with its 8640D and 8641D Power Architecture processors – both of which are offered by GE Fanuc. The 8641D features two cores operating at 1.5GHz and dissipates only 32 watts (While, superficially, this compares unfavourably with the clock speed of Intel’s dual core offering, it should be remembered that there are many factors beyond clock speed that contribute to overall processor performance.) The 8640D offers comparable performance to the 8641D, but with a much lower 22 watts of heat dissipation.

Already, the market is seeing quad core processors. Intel began announcing Core2 Quad processors a year ago, and Freescale has responded with its QorIQ family of processors. Based around the Power Architecture e500mc core and retaining software compatibility with the PowerPC platform, QorIQ uses a 45nm process (with a roadmap to 32nm) and is planned to support up to eight cores. Freescale’s goal, it is said, is to bring in these high performance processors within a power envelope of 30 watts – music to the ears of many military embedded computing developers. Inevitably, ‘real world’ products featuring latest generation processors lag processor announcements by many months.

And yes, 16-core processors are already on the horizon. Coming, no doubt, to a single board computer near you. To find out more about GE Fanuc’s latest multicore offering, visit us here.