Even though AMD and now GlobalFoundries always cited that SOI [Silicon-On-Insulator] brings significant power savings on AMD microprocessor architecture – in the tune of 30%, not a lot of companies decided to manufacture their chips using SOI wafers. Besides AMD CPUs, we also have IBM’s PowerPC chips and STI’s Cell processor [again, PowerPC based] – not a great number of customers, to say the least.
The reason for that might be the lack of spare SOI capacity, but with the owner of GlobalFoundries snapping up Chartered Semiconductor the future is looking brighter. On IEEE SOI Conference in Foster City, ARM announced the results of its 45nm silicon-on-insulator test chip. As expected, usage of SOI wafer significantly reduced the power consumption over the conventional bulk process. The test itself is a fruition of efforts made by the ARM’s Physical IP division, headed by Tom Lantzsch. According to Tom, ARM was always proposing SOI to its customers but often fell on deaf ears over lack of physical evidence.
In case of ARM 1176 core, similar to the ARM core used in nVidia Tegra chip and Texas Instruments OMAP chips – power savings were as high as 40%. The goal of the test was comparison between 45nm SOI high-performance and 45nm bulk Low-Power process, clearly demonstrating that even a non-power optimized, high-performing SOI process can result in significant power savings and enable a large jump in performance inside the same thermal envelope. When ARM’s engineers overclocked the 45nm SOI chip by 20%, the chip still saved 30% over the standard bulk silicon, meaning you could clock ARM core significantly higher and still achieve remarkable power savings.
Power saving was not the only benefit of switching to SOI, though – ARM reported a seven percent "circuit area reduction", meaning you can build even smaller chips. With Intel talking about Light Peak optical connectivity and having already demonstrated a SOI wafer for silicon laser demonstration back in 2006, we feel that you’ll be starting to hear a lot of SOI-related news during 2010 and onwards. Quite the opposite of "SOI is dead" mantra we heard from Intel and other bulk silicon vendors since the beginning of 2001.
If SOI expands into low-power devices, it will be only the matter of time before GlobalFoundries starts making more low-power SOI chips than they do big ones [first in volume only, then we can debate on die space].