Trying to disable Processor idle states (C states) on Windows PC

You can use SetThreadExecutionState function which enables the application to inform the system that it is in use.

EDIT: After a little research and testing I came to a solution or I think I did. You're on the right track for Windows XP. If you read the documentation for the PROCESSOR_POWER_POLICY structure , you'll notice you can disable each C-states that offends you:

Policy[0].AllowPromotion = 0; // Disable's C1 (usually C1 won't cause problems, so you should leave it alone.)Policy[1].AllowPromotion = 0; // Disable's C2Policy[2].AllowPromotion = 0; // Disable's C3

In Vista and Windows7 you can't use this interface instead you have to do this:

GUID *scheme;PowerGetActiveScheme(NULL, &scheme); PowerWriteACValueIndex(NULL, scheme, &GUID_PROCESSOR_SETTINGS_SUBGROUP,  &GUID_PROCESSOR_IDLE_DISABLE, 1); PowerSetActiveScheme(NULL, scheme);

I haven't found a way to disable individual C states on Vista and Windows 7. If you need some sample codes please email me I can help you out.

This seems to be working for me:

void PowerState(bool bEnable){    // CPU idle state    unsigned int ActPwrSch;    MACHINE_PROCESSOR_POWER_POLICY Policy;    if (GetActivePwrScheme(&ActPwrSch))    {        if (ReadProcessorPwrScheme(ActPwrSch, &Policy))        {            Policy.ProcessorPolicyAc.Policy[0].AllowPromotion = bEnable ? 1: 0; // C1            Policy.ProcessorPolicyAc.Policy[1].AllowPromotion = bEnable ? 1: 0; // C2            Policy.ProcessorPolicyAc.Policy[2].AllowPromotion = bEnable ? 1: 0; // C3            if (WriteProcessorPwrScheme(ActPwrSch, &Policy))                SetActivePwrScheme(ActPwrSch, 0, 0);        }    }    OSVERSIONINFO osvi;    memset(&osvi, 0, sizeof(OSVERSIONINFO));    osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);    GetVersionEx(&osvi);    // For Vista and above    if (osvi.dwMajorVersion >= 6)    {        static const GUID processor_idle_disable_guid = {0x5d76a2ca, 0xe8c0, 0x402f, 0xa1, 0x33, 0x21, 0x58, 0x49, 0x2d, 0x58, 0xad};        GUID *scheme;        PowerGetActiveScheme(NULL, &scheme);        PowerWriteACValueIndex(NULL, scheme, &GUID_PROCESSOR_SETTINGS_SUBGROUP, &processor_idle_disable_guid, bEnable ? 0 :  1);        PowerSetActiveScheme(NULL, scheme);    }}

Surely a TSR running a mathematical calculation every 5 minutes will prevent an idle state?Alternatively you can purchase a cheap hardware or software mouse emulator that sends a mouse move signal at defined intervals.