A Brief History

In the days when most musicians ran Windows 95, 98 or ME, the question of running multiple processors didn’t arise, because none of these operating systems supported more than a single CPU. It was Windows NT and then Windows 2000 that introduced us to the benefits of being able to share the processing load between multiple CPUs: Windows 2000 Professional supported one or two processor chips, while the more expensive Server version supported up to four, and the Advanced Server up to eight. However, at this early stage each processor was a physically separate device, so to be able to (for instance) use twin processors, you needed a specially designed motherboard with two CPU sockets. Many audio developers and interface manufacturers didn’t actively support Windows 2000, so most musicians stuck with Windows 98.
In 2001, Microsoft released Windows XP in Home and Professional versions, and once again most consumers who opted for the Home version were limited to a single physical processor, although the Professional version supported two. By this stage many musicians were straining at the leash, wanting to run more and more plug-ins and software instruments, and this Professional version let them do exactly that, using dual-processor motherboards and twin Xeon or Pentium 4 processors.When you’re running stereo audio editors (such as Wavelab 6, shown here) and stand-alone soft synths or samplers, and even in most multitrack sequencers when you’re only running a single track, only one core of a multi-core CPU will be heavily used, although any others available may help with disk access, the user interface and other applications that are running simultaneously.
Multi-processing options really opened up the following year, when Intel introduced first Xeon and then Pentium 4C processor ranges with Hyperthreading technology, which let these CPUs appear to both Windows XP Home and Professional (or Linux 2.4x) as two ‘virtual’ processors instead of one physical one. They each shared the various internal ’sub-units’, including the all-important FPU (Floating Point Unit), but could run two separate processing ‘threads’ simultaneously.

Intel claimed up to a 30 percent improvement with specially written applications over a standard processor, but as many musicians soon found, having a Hyperthreaded processor didn’t necessarily benefit them at all unless they were running several applications simultaneously, since applications like MIDI + Audio sequencers had to be rewritten to take advantage of Hyperthreading. Steinberg’s Nuendo 2 was one of the few music apps to support it, but although various others followed, a few (such as Tascam’s Gigastudio) needed a major rewrite before they would even run with HT enabled. Nevertheless, my own tests (published in PC Notes June 2004) showed that with optimised audio applications such as Cubase SX2 you could expect a significant drop in CPU overheads where it really mattered, at low latencies of 3ms or under.
The biggest change came in late 2004, when both AMD and Intel seemed to agree that processor clock speeds had reached a ceiling. Intel abandoned plans to release a 4GHz model in their Prescott CPU range, and in 2005 both companies largely switched to releasing dual-core models. Unlike the twin virtual processors of Intel’s Hyperthreading range, these featured two separate processing chips mounted inside one physical package. By placing two processor cores into a single piece of silicon, manufacturers could provide significantly faster performance than a single processor, even when under-clocking them and running them at lower voltages, so that they didn’t run hotter than the single-core variety.
By late 2006 we had been introduced to quad-core processors, which have now dropped in price and can even be run with Windows XP Home (which is licensed to run a single physical processor, however many cores it has inside). However, if running XP Professional (and the x64 64-bit version), Vista Home Premium, Business, Enterprise or Vista Ultimate you also gain the option of installing two quad-core processors on a suitable motherboard, to provide a total of eight processing cores. Unfortunately, as with so many new hardware advancements, much software has had a long way to catch up before it could take advantage of so many cores.