5137ch02.fm
Draft Document for Review October 14, 2014 10:19 am
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IBM Power Systems E870 and E880 Technical Overview and Introduction
Table 2-10 Power E870 single core bandwidth estimates
The bandwidth figures for the caches are calculated as follows:
L1 cache: In one clock cycle, two 16-byte load operations and one 16-byte store operation
can be accomplished. The value varies depending on the clock of the core and the formula
is as follows:
– 4.024 GHz Core: (2 * 16 B + 1 * 16 B) * 4.024 GHz = 193.15 GBps
– 4.190 GHz Core: (2 * 16 B + 1 * 16 B) * 4.190 GHz = 201.12 GBps
L2 cache: In one clock cycle, one 32-byte load operation and one 16-byte store operation
can be accomplished. The value varies depending on the clock of the core and the formula
is as follows:
– 4.024 GHz Core: (1 * 32 B + 1 * 16 B) * 4.024 GHz = 193.15 GBps
– 4.190 GHz Core: (1 * 32 B + 1 * 16 B) * 4.190 GHz = 201.12 GBps
L3 cache: In one clock cycle, one 32-byte load operation and one 32-byte store operation
can be accomplished. The value varies depending on the clock of the core and the formula
is as follows:
– 4.024 GHz Core: (1 * 32 B + 1 * 32 B) * 4.024 GHz = 257.54 GBps
– 4.190 GHz Core: (1 * 32 B + 1 * 32 B) * 4.190 GHz = 286.16 GBps
For each system node of a Power E870 populated with four processors and all its memory
CDIMMs filled, the overall bandwidths are shown in Table 2-11.
Table 2-11 Power E870 system node bandwidth estimates
PCIe Interconnect: Each POWER8 processor has 32 PCIe lanes running at 7.877Gbps
full-duplex. The bandwidth formula is calculated as follows:
32 lanes * 4 processors * 7.877 Gbps * 2 = 252.064 GBps
Single core
Power E870
Power E870
1 core @ 4.024 GHz
1 core @ 4.190 GHz
L1 (data) cache
193.15 GBps
201.12 GBps
L2 cache
193.15 GBps
201.12 GBps
L3 cache
257.54 GBps
268.16 GBps
System node bandwidths
Power E870
Power E870
32 cores @ 4.024 GHz
40 cores @ 4.190 GHz
L1 (data) cache
6,181 GBps
8,045 GBps
L2 cache
6,181 GBps
8,045 GBps
L3 cache
8,241 GBps
10,726 GBps
Total Memory
922 GBps
922 GBps
PCIe Interconnect
252.064 GBps
252.064 GBps
Intra-node buses
(two system nodes)
922 GBps
922 GBps
Rounding: The bandwidths listed here may appear slightly differently in other materials
due to rounding of some figures.
