1.2 Alternative Cache Organizations
Phased caches first access the tag and then the data arrays.
Only the hit data way is accessed in the second phase, resulting
in less data way access energy at the expense of longer access
time. Researchers recently proposed the way concatenation
technique for reducing dynamic cache power for application specific
systems. The cache can be configured by software to be
a direct-mapped, two-way or four-way set-associative cache so as
to save power. The MNM mechanism is proposed to discover
cache misses early so that power consumption of the cache can be
saved. CAM-tagged caches are often used in low-power systems.
A CAM based cache puts one set of a cache in a small sub-bank
and uses a CAM for the tag lookup of that set. A set may have 32
or even 64 ways. However, the CAM tags must be searched before
the data can be retrieved, which increases the cache latency. The
area overhead brought by CAM cells is also not negligible.