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Summary: Appears in 34th Annual International Symposium on Microarchitecture, MICRO-34, Austin, Texas, December 2001 1
Direct Addressed Caches for Reduced Power Consumption
Emmett Witchel, Sam Larsen, C. Scott Ananian and Krste Asanovi´c
MIT Laboratory for Computer Science, Cambridge, MA 02139
witchel|slarsen|cananian|krste @lcs.mit.edu
Abstract
A direct addressed cache is a hardware-software design
for an energy-efficient microprocessor data cache. Direct
addressing allows software to access cache data without a
hardware cache tag check. These tag-unchecked loads and
stores save the energy of a tag check when the compiler can
guarantee an access will be to the same line as an earlier
access. We have added support for tag-unchecked loads and
stores to C and Java compilers. For Mediabench C pro-
grams, the compiler eliminates 1676% of data cache tag
accesses, with half of the benchmarks avoiding over 40%
of the data tag checks. For SPECjvm98 Java programs,
the compiler eliminates 1863% of data cache tag checks.
These tag check reductions translate into data cache energy
savings of 940%, and overall processor and cache energy
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