Pollack's Rule
Encyclopedia
Pollack's Rule states that microprocessor
"performance increase due to microarchitecture advances is roughly proportional to [the] square root of [the] increase in complexity". This contrasts with power consumption increase, which is roughly linearly proportional to the increase in complexity. Complexity in this context means processor logic, i.e its area.
The rule, which is an industry term, is named for Fred Pollack, a lead engineer and fellow at Intel.
Pollack's Rule gained increasing relevance in 2008 due to the broad adoption of multi-core computing and concern expressed by businesses and individuals at the huge electricity demands of computers.
A generous interpretation of the rule allows for the case in which an ideal device could contain hundreds of low-complexity cores, each operating at very low power and together performing large amounts of (processing) work quickly. This describes a massively parallel processor array
(MPPA), which is currently being used in embedded systems and accelerators.
, each new technology generation doubles the number of transistors on chip increasing performance by 40%. On the other hand, Pollack's rule implies that microarchitecture advances improve the performance by another 40%. Therefore, the overall performance increase is roughly two-fold, while the power consumption stays the same. In practice, however, implementing new microarchitecture every new generation is difficult, so microarchitecture gains are typically less.
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
"performance increase due to microarchitecture advances is roughly proportional to [the] square root of [the] increase in complexity". This contrasts with power consumption increase, which is roughly linearly proportional to the increase in complexity. Complexity in this context means processor logic, i.e its area.
The rule, which is an industry term, is named for Fred Pollack, a lead engineer and fellow at Intel.
Pollack's Rule gained increasing relevance in 2008 due to the broad adoption of multi-core computing and concern expressed by businesses and individuals at the huge electricity demands of computers.
A generous interpretation of the rule allows for the case in which an ideal device could contain hundreds of low-complexity cores, each operating at very low power and together performing large amounts of (processing) work quickly. This describes a massively parallel processor array
Massively parallel processor array
A Massively Parallel Processor Array is a type of integrated circuit which has a massively parallel array of hundreds or thousands of CPUs and RAM memories. These processors pass work to one another through a reconfigurable interconnect of channels...
(MPPA), which is currently being used in embedded systems and accelerators.
Implications of the rule on chip performance
According to Moore's lawMoore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
, each new technology generation doubles the number of transistors on chip increasing performance by 40%. On the other hand, Pollack's rule implies that microarchitecture advances improve the performance by another 40%. Therefore, the overall performance increase is roughly two-fold, while the power consumption stays the same. In practice, however, implementing new microarchitecture every new generation is difficult, so microarchitecture gains are typically less.