eWEEK at 30: Multicore CPUs Keep Chip Makers in Step With Moore's Law

By Jeff Burt  |  Posted 2014-02-20 Print this article Print

AMD had a plan in place for eventually getting to two cores with its initial Opterons, according to Insight 64's Brookwood. The company had designed the Opteron to make an easy transition to dual-core as the transistors shrunk, and two years after releasing its first Opteron, a two-core version was ready.

"AMD had a much cleaner architecture solution, and it allowed AMD to have an advantage over Intel [initially]," he said.

Intel's initial dual-core chip was essentially a two-die, multichip package with a shared memory interface, Brookwood said. And where Intel initially relied on a front-side bus to connect to memory, AMD's chips offered an integrated memory controller, which officials said gave the Opteron and Athlon chips a performance advantage over the Intel products. However, Intel officials have argued that the decision to stay at first with the front-side bus was made to address the balance needed in the chips between the cores and the bandwidth to the memory and I/O in order to realize the best performance.

Intel has since put integrated memory controllers into its chips and also uses the QuickPath Interconnect technology in conjunction with the controllers for better performance and scalability.

Since the first x86 dual-core chips were introduced in 2005, the number of cores on processors has grown rapidly. AMD officials in January launched new Opterons in the 6300 family that hold 12 and 16 cores. Meanwhile, Intel executives on Feb. 18 unveiled the high-end Xeon E7 v2 "Ivytown" server chips, which offer up to 15 cores and hold more than 4.3 billion transistors.

Initially, the biggest challenge for multicore chips was not the hardware but the software, according to Brookwood. There were few applications then that could take advantage of chips with multiple cores, so organizations weren't always seeing performance gains in their software by using systems with dual cores.

"You would run [the application] on a multicore machine and get half the performance of the multicore machine because the second core was sitting there just twiddling its thumbs," he said. "The issues in adopting multicore processors are almost entirely software-related."

Now most software is written to take advantage of multicore chips, Brookwood said. Even the low-end servers have two to four cores in them, and most PCs also run multicore chips. Vendors are even making chips for smartphones that have as many as four cores, and future plans are calling for eight or more.

Intel's Bajwa said that in the server world, a lot of cores make sense.

"In the server space, a lot of applications can benefit from a lot of cores," he said. "The server case is fairly solid, and the ecosystem can use them quite well."


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