Processor activation

How many processor activations are needed when configuring a Power Systems model 780 or 795 that will run in TurboCore mode, and what is the impact to the activations if an IPL is performed to switch the machine between TurboCore and MaxCore modes?

In TurboCore mode up to half of the processor cores on each single-chip module (SCM) are disabled and their L3 cache is made available to the active processor cores on the chip, which provides a performance boost to the active cores. In general, the number of cores used in TurboCore mode is equal to the number of processors activated, but only up to a maximum of half the number of cores physically installed. To order a system which will run in TurboCore mode, you need to configure extra processor cores since at most only half of them are used, but you don’t need to configure extra activations. Consider the following examples:

• Example 1. A server has 32 physical processor cores with 14 activated, running in TurboCore mode. If you re-IPL the system and switch to MaxCore mode, you now have 14 processor cores running in MaxCore mode.

• Example 2. A server has 32 physical processor cores with 14 activated, running in MaxCore mode. If you re-IPL the system and switch to TurboCore mode, you now have 14 processor cores running in TurboCore mode.

• Example 3. A server has 48 physical processor cores with 21 activated, running in MaxCore mode. If you re-IPL the system and switch to TurboCore mode, you will have 21 processors running in TurboCore mode. There is no requirement to have an even number of processors running in TurboCore mode.

• Example 4. A server has 48 physical processor cores with 29 activated, running in MaxCore mode. If you re-IPL the system and switch to TurboCore mode, you will have 24 processors running in TurboCore mode and 5 extra activations which are not used, because the maximum number of cores that can be used in TurboCore mode is half the number of cores physically installed (24 out of 48 in this case).

The rules for the minimum number of processor activations still apply when configuring an initial order model 780 or 795 for TurboCore mode. On a model 780 at least 4 processor cores must be activated. On a model 795, you must have a minimum of three #4700 processor books for TurboCore mode support (96 cores), and you must activate a minimum 25% or 24 of the installed processor cores, whichever is greater. The TurboCore specify feature code #9982 instructs IBM to set up the new server in TurboCore mode.

Note that e-config allows you to configure a new 780 or 795 server with a TurboCore specify feature and a quantity of processor activations that is greater than half the number of physical processors configured. The excess processor activations cannot be used while the system is in TurboCore mode, but would be available if the system was changed to MaxCore mode via an IPL.