SPEC CPU2006 Flag Description - Platform settings
- Utilization Profile:
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This BIOS switch allows 2 options: "Even" and "Unbalanced". The default is "Even"
and the best choice for all workloads utilizing the whole system. In cases where
the utilization is highly concentrated on few resources of the system the
performance of the application could be improved by setting to "Unbalanced".
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Setting this option to "Unbalanced" may improve performance but also
increase the power consumption of the system. Users should only select
this option after performing application benchmarking to verify improved
performance in their environment.
- Energy Performance:
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This BIOS switch allows 4 options: "Balanced performance", "Performance",
"Balanced Energy" and "Energy Efficient". The default is "Balanced Performance"
optimized to maximum power savings with minimal impact on performance.
"Performance" disables all power management options with any impact on performance.
"Balanced Energy" is optimized for power efficiency and "Energy Efficient" for
power savings. The BIOS switch is only selectable if the BIOS switch
"Power Technology" is set to "Custom".
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The two options "Balanced Performance" and "Balanced Energy" should always be the
first choice as both options optimize the efficiency of the system. In cases where
the performance is not sufficient or the power consumption is too high the two
options "Performance" or "Energy Efficient" could be an alternative.
- QPI snoop mode:
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There are 3 snoop mode options for how to maintain cache coherency across the Intel QPI fabric,
each with varying memory latency & bandwidth characteristics depending on how the snoop traffic is generated.
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There are 2 BIOS switches to select one of these 3 modes.The corresponding settings are given below together with the description of the 3 snoop modes.
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Cluster on Die
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(BIOS switch settings to enable this mode: "COD Enable" = Enabled and "Early Snoop" = Disabled)
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This mode logically splits a socket into 2 NUMA domains that are exposed to the OS with half the amount of cores
& LLC assigned to each NUMA domain in a socket.
This mode utilizes an on-die directory cache & in memory directory bits to determine whether a snoop needs to be sent.
Use this mode for highly NUMA optimized workloads to get the lowest local memory latency & highest local memory bandwidth for NUMA workloads.
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In "Home Snoop" and "Early Snoop" modes, snoops are always sent -- they just originate from different places:
the caching agent (earlier) in "Early Snoop" mode and the home agent (later) in "Home Snoop" mode.
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Home Snoop
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(BIOS switch settings to enable this mode: "COD Enable" = Disabled and "Early Snoop" = Disabled)
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Use Home Snoop mode for NUMA workloads that are memory bandwidth sensitive and need both local & remote memory bandwidth.
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Early Snoop
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(BIOS switch settings to enable this mode: "COD Enable" = Disabled and "Early Snoop" = Enabled)
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Use Early Snoop mode for workloads that are memory latency sensitive or for workloads that benefit from fast cache-to-cache transfer latencies from the remote socket.
Snoops are sent out earlier, which is why memory latency is lower in this mode.
- CPU C1E Support
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Enabling this option which is the default allows the processor to transmit to its
minimum frequency when entering the power state C1. If the switch is disabled the
CPU stays at its maximum frequency in C1. Because of the increase of power
consumption users should only select this option after performing application
benchmarking to verify improved performance in their environment.
- QPI Link Frequency Select
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This switch allows the configuration of the QPI link speed. Default is auto, which
configures the optimal link speed automatically.