Cooling Codes: Thermal-Management Coding for High-Performance Interconnects

Abstract

High temperatures have dramatic negative effects on interconnect performance and, hence, numerous techniques have been proposed to reduce the power consumption of on-chip buses. However, existing methods fall short of fully addressing the thermal challenges posed by high-performance interconnects. In this paper, we introduce new efficient coding schemes that make it possible to directly control the peak temperature of a bus by effectively cooling its hottest wires. This is achieved by avoiding state transitions on the hottest wires for as long as necessary until their temperature drops off. We also reduce the average power consumption by making sure that the total number of state transitions on all the wires is below a prescribed threshold. We show how each of these two features can be coded for separately or, alternatively, how both can be achieved at the same time. In addition, error-correction for the transmitted information can be provided while controlling the peak temperature and/or the average power consumption.In general, our cooling codes use n > k wires to encode a given k-bit bus. One of our goals herein is to determine the minimum possible number of wires n needed to encode k bits while satisfying any combination of the three desired properties. We provide full theoretical analysis in each case. In particular, we show that n = k + t + 1 suffices to cool the t hottest wires, and this is the best possible. Moreover, although the proposed coding schemes make use of sophisticated tools from combinatorics, discrete geometry, linear algebra, and coding theory, the resulting encoders and decoders are fully practical. They do not require significant computational overhead and can be implemented without sacrificing a large circuit area.

Low-Power Cooling Codes with Efficient Encoding and Decoding

“…Chee et. al [3] also proposed the following constructions of LPC codes which have efficient coding schemes.…”

“…Asymptotically, the codes obtained by the construction attain the bound of Theorem 5. As was mentioned before, there are three types of constructions for LPC codes in [3]. The first one is based on decomposition of the complete hypergraph, the second one is a concatenation method based on q-ary cooling codes, and the third one is a Sunflower Construction.…”

“…For this reason, thermally-aware approaches have emerged as one of the most important domains of research in chip design today. Numerous techniques have been proposed to reduce the overall power consumption of on-chip buses (see [3] which uses coding techniques and the references therein using non-coding techniques). However, all the non-coding techniques do not directly address peak temperature minimization.…”

“…. , C M as codesets and the vectors in them as codewords.Using partial spreads, Chee et al [3] constructed LPC codes with efficient encoding and decoding schemes.When t ≤ 0.687n and w ≥ (n − t)/2, these codes achieve optimal asymptotic rates. However, when w is small, i.e.…”

“…Using partial spreads, Chee et al [3] constructed LPC codes with efficient encoding and decoding schemes.…”