EIST is software-controlled!

[VirtualLarry]

From here

6.2.8 Enhanced Intel SpeedStep® Technology
The processor supports Enhanced Intel SpeedStep Technology. This technology enables
the processor to switch between frequency and voltage points, which may result in
platform power savings. To support this technology, the system must support dynamic
VID transitions. Switching between voltage/frequency states is software controlled.
Enhanced Intel SpeedStep Technology is a technology that creates processor
performance states (P states). P states are power consumption and capability states
within the Normal state as shown in Figure 17. Enhanced Intel SpeedStep Technology
enables real-time dynamic switching between frequency and voltage points. It alters
the performance of the processor by changing the bus to core frequency ratio and
voltage. This allows the processor to run at different core frequencies and voltages to
best serve the performance and power requirements of the processor and system. Note
that the front side bus is not altered; only the internal core frequency is changed. In
order to run at reduced power consumption, the voltage is altered in step with the bus
ratio.
The following are key features of Enhanced Intel SpeedStep Technology:
? Voltage/Frequency selection is software controlled by writing to processor MSR's
(Model Specific Registers), thus eliminating chipset dependency.
? If the target frequency is higher than the current frequency, Vcc is incremented
in steps (+12.5 mV) by placing a new value on the VID signals after which the
processor shifts to the new frequency. Note that the top frequency for the
processor can not be exceeded.
? If the target frequency is lower than the current frequency, the processor shifts
to the new frequency and Vcc is then decremented in steps (-12.5 mV) by
changing the target VID through the VID signals.

This makes me wonder - does EIST function in Windows XP? Does it have a driver for EIST support in desktop C2Ds?

This also makes me wonder about C1E support - is that also software-controlled, or is that handled by hardware?

Edit: That makes me remember - if you are using XP, then you need to download and install an updated AMD CnQ driver if you are using an AMD CPU and have CnQ enabled in BIOS. So is there an updated EIST driver for Intel systems?

 

[taltamir]

C1E = enhanced halt = automatically reduce multiplier and voltage (only if not modified from VID, personally i never say it reduce voltage), controlled by CPU's internal logic.
EIST = speed step = software / drivers can modify the speed, voltage, etc. Useful from OCing from within the OS, or for running dynamic energy saving programs (like gigabyte DES), or just letting windows itself (if a modern enough version) mess with it.