9-13
PERFORMANCE CONSIDERATIONS
Figure 9-5. L2 Cache Performance Data with One Write Buffer
9.6.4 Impact of Second-Level Cache on Bus Utilization
A second-level cache reduces the number of processor reads to main memory, lowering external
system bus utilization. The benefit is more bandwidth available to other bus master devices like
DMA or LAN controllers. Systems with multiple CPUs are sensitive to the amount of bus band-
width used by each CPU. Note that with a write-through cache the minimum bus bandwidth is
the number of writes performed.
0.0
0.1
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0.3
0.2
3-1-3 Page Hit
5-1-4
4-2-4 Page Hit
7-1-5 Page Miss
7-2-5 Page Miss
L2 Cache Performance Data with One Write Buffer
Intel486™ CPU without L2 cache
64 K
128 K
256 K
Relative Performance to 2-1-2 Memory
Note: The performance figures are approximations.
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