setting MSR 0x1AD (turbo ratio limits) has no effect on Sandy Bridge

[idata]

Setting MSR 0x1AD in windows does not change the maximum turbo ratio limit as http://www.intel.com/content/www/us/en/processors/xeon/intel64-ia32-architectures-manual-vol3.html?wapkw=software%20developer%27s%20manual http://www.intel.com/content/www/us/en/processors/xeon/intel64-ia32-architectures-manual-vol3.html?wapkw=software%20developer%27s%20manual says it should, even if MSR_PLATFORM_INFO bit 28 is high. The processor does not even respond to lowering the turbo ratio limit. This has proven true numerous times on multiple Sandy Bridge based systems.

It seems that the CPU is not bothering to read the MSR and set itself to the new value. Does anyone have an idea on what must be done to force the CPU to change its maximum turbo ratio limit while the system is in Windows or another OS?

[idata]

No one reply yet? I want to know too.

[idata]

Just an update on things that I've tried. I have set the turbo ratio limit MSR, then rebooted, but the register would get reset. I have set the MSR, put computer to sleep, and resumed, but the register would be reset. I have booted with turbo disabled, set the MSR, then enabled turbo, but there was no change in the turbo limit.

Also, desktop users who have P67 PCHs (which allow unlimited overclocking in BIOS) have the same results as me when trying to change turbo ratio limits after the system has booted.