Intel EIST (Speedstep), enable or disable?

[grimpr]

Since Nehalem Intel uses power gating that completely shuts down the cores etc, Sandy Bridge is even more aggressive than Nehalem and comes very quick down to Idle and C6. Whats the real advantage for EIST at least for Desktops since the Cores quickly go down to idle and C6? I found out that when i disabled EIST i noticed an immediately more responsive and snappy desktop experience with the essential power saving features, power gating and c6, still on, the CPU goes full speed and comes down to idle very quick saving more power in the process than using the intermediatery frequency scaling steps of EIST. Really, whats the advantage of enabling it? Its archaic and comes from the Pentium M era, its of no use anymore at least for me and my desktops.

 

[ShintaiDK]

EIST is the first step of idle mode. Then C1E with instruction halt.

Also I cant feel the difference with it enabled or not. We talk nanoseconds here.

So always enable it.

EIST started as V1.1 in P3. Core 2 for example had V3.2

So its not exactly archanic.

Without EIST you would burn alot of power in idle.

 

[grimpr]

No its not "Idle mode", it justs scales the frequency according to load using p-states, C1E and C6 work independently along with Core Power Gating at least in my ASUS board, the experience on the desktop on a SB Core i3 with EIST disabled was easily noticed by me, more snappy experience, the CPU doesnt play around with lower frequencies anymore due to EIST, it goes full speed, idles down very fast and gives a more fluid experience.

 

[ShintaiDK]

No its not "Idle mode", it justs scales the frequency according to load using p-states, C1E and C6 work independently along with Core Power Gating at least in my ASUS board, the experience on the desktop on a SB Core i3 with EIST disabled was easily noticed by me, more snappy experience, the CPU doesnt play around with lower frequencies anymore due to EIST, it goes full speed, idles down very fast and gives a more fluid experience.

Whats the powerconsumption at say 3.4Ghz for an i5 2500K and 1.6Ghz? I consider that idle worthy. Also the voltage gets reduced too.

If you got Asus, make sure you disable the EPU.

 

[grimpr]

Yes i understand what you say. You believe that disabling EIST completely disables all power saving features of the CPU, thats not true anymore at least on Sandy Bridge, you can find out for yourself by disabling EIST on BIOS and checking with CPU-Z for your voltages and frequencys with EIST On & Off, you will find that even with EIST disabled the CPU comfortably idles with reduced voltages at its designated idle speed, lets say 1600mhz, and quickly goes to full speed, 3400mhz, even on small loads skipping the intermediate pstate frequencies of EIST, like 2400mhz etc. It makes a difference...

 

[borisvodofsky]

Yes i understand what you say. You believe that disabling EIST completely disables all power saving features of the CPU, thats not true anymore at least on Sandy Bridge, you can find out for yourself by disabling EIST on BIOS and checking with CPU-Z for your voltages and frequencys with EIST On & Off, you will find that even with EIST disabled the CPU comfortably idles with reduced voltages at its designated idle speed, lets say 1600mhz, and quickly goes to full speed, 3400mhz, even on small loads skipping the intermediate pstate frequencies of EIST, like 2400mhz etc. It makes a difference...

Ah... if you disable EIST, the computer will run a static multiplier, whatever you set for the turbo multiplier, it will stick to it. the voltage will also reflect that.


If you are running a lower end CPU, this is fine. But with heavily overclocked CPUs, this isn't advised. 😉

 

[IntelUser2000]

Really, whats the advantage of enabling it? Its archaic and comes from the Pentium M era, its of no use anymore at least for me and my desktops.

It's still valid, and just as important. EIST allows applications that do not need full capability of the chip to use less power. That's probably not a big deal in full-scale desktops, but for mobile it is.

Some say that full computing power of the top desktop chips like the 2600K is wasted in light load. Well, guess what, it won't run at full speed for those light apps. Of course, it also depends on the developers to make their applications run at those speeds rather than full.