Sun, IBM push multicore boundaries

Colors of Sun's Rainbow
Sun's Rainbow Falls will require about 30 percent more power than the previous generation called T2+ which integrated eight cores. However, the new chip—built in a 40nm TSMC process--is about the same size as the T2+.

Sun's Rainbow Falls puts 16 cores on a two level crossbar switch. Click on image to enlarge.

Sanjay Patel, a senior Sun architect who presented the Hot Chips paper, said putting 16 cores on a general-purpose server chip was an industry first. "Integrating 16 cores is a challenge in chip design, and we had to iterate several times to come up with an architectural spec," he said.

The design uses a credit-based flow control scheme to manage as many as 1,024 outstanding transactions per chip. The design uses the same basic core Sun employed on the previous T2 chip, but it enhanced its floating-point unit and added new block ciphers and hash functions to an embedded cryptographic accelerator.

"Security is one area where the Sun design shines most because they can enable these features in their Solaris operating system," said analyst Glaskowsky, differentiating themselves from lower cost x86-based PC servers.

The Power7 core is a new design sporting 12 execution units. It is a smaller, lower frequency core than the one on the Power6 but offers higher performance.

These are cores that by themselves would create a very powerful computer," said William Starke, an architect on Power7.

At the chip level, IBM claims Power7 will deliver four times the performance of Power6, thanks to the combination of expanded, cache and interconnects.