Comparison to dell poweredge 11, Generation servers, Figure 9 – Dell PowerEdge 1655MC User Manual
Page 23: Impact of c states and c1e on remote memory access
Optimal BIOS settings for HPC with Dell PowerEdge 12
th
generation servers
23
Figure 9. Impact of C States and C1E on remote memory access
* Data collected on a single PowerEdge M620, Dual Intel Xeon E5-2680 @ 2.7GHz, 8*8GB 1600MT/s
memory. Logical Processor and Node Interleaving Disabled. Performance CPU Power Management. Turbo
Enabled.
From the chart it is seen that when C States and C1E are disabled, remote memory bandwidth is
24% faster compared to when C States and C1E are enabled. This penalty for remote accesses will
not be incurred if all system cores are active; it is only a factor when the remote cores are idle and
in deep sleep states.
Thus for applications that may not utilize all system cores but are memory sensitive, it is
recommended to disable C States and C1E for best performance. This is in line with the
recommendations for latency sensitive applications in Section 3.5.
6. Comparison to Dell PowerEdge 11
th
generation servers
A similar study was performed with Dell’s previous generation servers when those servers were first
released.
11
Dell’s 11
th
generation product line includes servers that support the Intel Xeon 5500 series
processor (code named Nehalem-EP). In this section the results of the previous study are compared to
the results presented in this document.
Details of the two test beds are in Table 6. As is obvious from the table, the test clusters are not
identical. However, each cluster was configured with the best choices available at the time. In the
earlier time frame, 1333MT/s memory was the top speed. With three memory channels per socket,
configuring 1 DIMM per channel for a total of 6 DIMMS in the server was considered optimal. With the
current generation, the cluster uses the top speed memory DIMMS, 1600 MT/s, and stays with 1 DIMM
per channel. But with the latest generation, this translates to 8 DIMMS per server.
24%
0
5
10
15
20
25
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M
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Impact of C states/C1E on remote bandwidth
C states/C1E Enabled
C states/C1E Disabled