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(a)
Read Energy
(b)
Write Energy
(c)
Static Energy
(d)
Average Energy
Fig. 6.
Energy reduction in cache operations
reading and writing energies of Flexicache is much lower than MS-ECC and trip-
lication. For the static energies (i.e. energy spent in one cycle when the cache is
idle), Flexicache presents slightly higher energy consumption than an unmodi-
fied cache mainly due to the additional extra slices (Figure. 6c). Note that these
additional slices also increase the cache capacity that we excluded this increased
capacity in our previous results. The static energy consumption of MS-ECC is
negligibly higher than a non-modified cache due to OLSC encoder/decoder. It
has been showed that dynamic energies are only the 30% of cache energy con-
sumptions and among them they are mostly (two out of three) read operations.
By considering that, in Figure 6d, we present the average energy consumption
of a cache at a time. The figure shows that only Flexicache can operate when
V
dd
is 320 mV by presenting 39% reduction in the energy consumption of the
cache compared to non-modified cache when it executes in the high-performance
mode with the minimum safe
V
dd
(i.e. 700 mV). MS-ECC can reduce the energy
consumption by only 5% compared to the same minimum safe voltage level.
Reliability against Particle Strike:
In Figure 7, we inject non-persistent,
multi-bit faults (i.e. size of the faults are between n=1-10 bits which means n
adjacent bit become faulty due to a particle strike) to the non-disabled cache
portion and, we present the fault coverage (i.e. the percentage of the injected
faults) for error detection (Figure 7a) and error correction (Figure 7b). In the
high-performance mode, MS-ECC can not detect or correct non-persistent faults
since it does not extend the cache lines with ECC codes. On the other hand,
each cache line is extended with ECC protection in the low-power mode when
