...to improve performance, Allen said. Among them:
- It's AMD's first chip with a built-in level-three cache. Cache memory can respond faster than main memory, and Intel has relied on large amounts of cache to improve its processors' performance. Each Barcelona core has its own 64KB (kilobyte) first-level data cache, 64KB first-level instruction cache and 512KB second-level cache; and the four cores together share a 2MB third-level cache, though AMD has said that size can be increased.
- AMD redesigned the Barcelona core, marking the biggest changes since the company made its 2003 transition from its 32-bit Athlon chips to the current 64-bit lineup. The magnitude of the transition is about halfway between the small tweaks AMD has made to Opteron over the years and the clean-sheet redesign Intel used in moving from NetBurst to its current Core design, Allen said.
- A faster floating-point engine performs mathematical calculations — long an Opteron strong suit, though not as important a part of the chip as that for integer operations. At a given clock frequency, a Barcelona core outperforms a current Opteron core by a factor of 1.8. By going quad-core, a Barcelona chip overall will provide a boost factor of 3.6, Allen said.
Not all things are better, though. Specifically, Barcelona's clock frequency will be lower than that for the company's dual-core chips. That's a common situation because quad-core chips require more circuitry, and more circuitry means more power consumption and waste heat, unless the chips run slower.
Read this
FAQ: Quad-core processing
The quad-core processor era was ushered in with the release of quad-core processors for enthusiasts and for servers and workstations in November 2006
AMD is moving its manufacturing from a 90nm (nanometre) process to a 65nm process, permitting more circuitry to fit in a given amount of chip real estate. Even with that change, the quad-core chips will run more slowly, Allen said. He argued that it's worth the tradeoff, though, since the additional cores can run more jobs simultaneously, even if an individual job isn't completed as swiftly.
"The slight degradation for frequency with quad-core will be overwhelmed by the increase in performance from dual-core to quad-core," Allen said. He declined to mention the chips' frequency.
