SPEC CPU2006 Flag Description - Platform settings

Firmware / BIOS / Microcode Settings

Utilization Profile:

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".

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:

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".

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.

Uncore Frequeny Override:

This BIOS switch allows 3 options: "Disabled", "Maximum" and "Nominal". The default is "Disabled" optimized for energy efficiency. "Maximum" sets the uncore frequency to the fixed maximum uncore frequency avaliable. "Nominal" reduces the uncore frequency to the nominal value.

Setting this option to "Maximum" 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.

QPI snoop mode:

There are 4 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.

There are 3 BIOS switches to select one of these 4 modes.The corresponding settings are given below together with the description of the 4 snoop modes.

Cluster on Die

(BIOS switch settings to enable this mode: "COD Enable" = Enabled and "Early Snoop" = Disabled and "Home Snoop Dir OSB" = Disabled)

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.

"Home Directory Snoop with OSB" is the Opportunistic Snoop Broadcast (OSB) directory mode. The HA can choose to do a speculative home snoop broadcast even before the directory information has been collected and checked.

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.

Home Snoop

(BIOS switch settings to enable this mode: "COD Enable" = Disabled and "Early Snoop" = Disabled and "Home Snoop Dir OSB" = Disabled)

Use Home Snoop mode for NUMA workloads that are memory bandwidth sensitive and need both local & remote memory bandwidth.

Early Snoop

(BIOS switch settings to enable this mode: "COD Enable" = Disabled and "Early Snoop" = Enabled and "Home Snoop Dir OSB" = Disabled)

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.

Home Directory Snoop with OSB

(BIOS switch settings to enable this mode: "COD Enable" = Disabled and "Early Snoop" = Disabled and "Home Snoop Dir OSB" = Enabled)

Use Home Directory Snoop with OSB under very lightly loaded conditions.

CPU C1E Support

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

This switch allows the configuration of the QPI link speed. Default is auto, which configures the optimal link speed automatically.