Note: Avanti’s Auto-Idle feature provides similar power saving functionality under both OpenVMS and Tru64 UNIX. See Auto-Idle for details.

Alpha CPU's were designed to run at 100% all the time. They do not have a reduced power mode like more modern Integrity and X86 processors. The exception is the processor used in the Tadpole, a laptop version of the Alpha. A hook was added to the firmware to signal the processor when VMS was not busy and temporarily pause the CPU by putting it into a low power state.

SRI (now Stomasys) developed the Idle Loop to take advantage of the Tadpole hook for Charon-AXP. They now call the Idle Loop the Idle Powersaver Driver and they explicitly warn against using it in production environments. See this link:

https://stromasys.atlassian.net/wiki/spaces/DocCHAXPSMAv2240W/pages/34603068/Idle+Powersaver+Driver

Avanti also supports the Idle Loop software with all its caveats. We’ve found the Idle Loop can have a substantial performance impact on application with high I/O thru put and low CPU utilization. If your applications are I/O intensive, we recommend disabling the Idle Loop. The Idle Loop can be disabled using the following command from the OpenVMS SYSTEM account, followed by a system reboot:

$ PRODUCT REMOVE IDLE

The Idle Loop can also be enabled and disabled using the system parameter LOAD_SYS_IMAGES. The default is 7. Changing it to 6 (clearing bit 0 = SGN$V_LOAD_SYS_IMAGES) prevents SYS$IDLE from being loaded during boot. See Removing Charon and HP Idle Utilities (OpenVMS Only) for instruction on removing the Idle Loop completely.