来源: 浣氬悕 2014-09-01


  Multicore Processors In 1965, when he first set out what we now call Moore’s Law, Gordon Moore said the number of components that

  could be packed onto an integrated circuit would double every year or so


  In 1971, Intel’s 4004 CPU had 2,300 transistors. In 1982, the 80286

  debuted with 134,000 transistors. Now, run-of-the-mill CPUs count upward

  of 200 million transistors, and Intel is scheduled to release a processor

  with 1.7 billion transistors for later this year.

  For years, such progress in CPUs was clearly predictable: Successive

  generations of semiconductor technology gave us bigger, more powerful

  processors on ever-thinner silicon substrates operating at increasing

  clock speeds. These smaller, faster transistors use less electricity, too.

  But there’s a catch. It turns out that as operating voltages get lower, a

  significant amount of electricity simply leaks away and ends up generating

  excessive heat, requiring much more attention to processor cooling and

  limiting the potential speed advance——think of this as a thermal barrier.

  To break through that barrier, processor makers are adopting a new

  strategy, packing two or more complete, independent processor cores, or

  CPUs, onto a single chip. This multicore processor plugs directly into a

  single socket on the motherboard, and the operating system sees each of

  the execution cores as a discrete logical processor that is independently

  controllable. Having two separate CPUs allows each one to run somewhat

  slower, and thus cooler, and still improve overall throughput for the

  machine in most cases.

  From one perspective, this is merely an extension of the design thinking

  that has for several years given us n-way servers using two or more

  standard CPUs; we’re simply making the packaging smaller and the

  integration more complete. In practice, however, this multicore strategy

  represents a major shift in processor architecture that will quickly

  pervade the computing industry. Having two CPUs on the same chip rather

  than plugged into two separate sockets greatly speeds communication

  between them and cuts waiting time.

  The first multicore CPU from Intel is already on the market. By the end of

  2006, Intel expects multicore processors to make up 40% of new desktops,

  70% of mobile CPUs and a whopping 85% of all server processors that it

  ships. Intel has said that all of its future CPU designs will be

  multicore. Intel’s major competitors——including Advanced Micro Devices

  Inc., Sun Microsystems Inc. and IBM——each appear to be betting the farm on

  multicore processors.

  Besides running cooler and faster, multicore processors are especially

  well suited to tasks that have operations that can be divided up into

  separate threads and run in parallel. On a dual-core CPU, software that

  can use multiple threads, such as database queries and graphics rendering,

  can run almost 100% faster than it can on a single-CPU chip.

  However, many applications that process in a linear fashion, including

  communications, backup and some types of numerical computation, won’t

  benefit as much and might even run slower on a dual-core processor than on

  a faster single-core CPU.