# Difference C1E and EIST?



## Laurijan (May 25, 2008)

Hi!

I read on the internet that C1E reduces multipier and voltage to CPU when the CPU is not used "much". 

Funny is that i read the same thing about EIST (SpeedStep), so why do i have both in my bios options if only one of them can be active and both are doing the same? 

Or can they be active at the same time, both working, but using differnt enery saving methods?

Lauri


----------



## largon (May 25, 2008)

Pages 10 & 11 in this document pretty much sums it up. No need to use both as they're almost the same but C1E is slightly better. 

EIST = allows performance steps
C1E = one single frequency & vCore step to minimum power state


----------



## Jarman (May 25, 2008)

C1E is slightly better at idle.

EIST has more steps though, so say if you are watching a 2 hour movie on both and the process is taking 25% cpu, C1E will have the VID and MHz at max and EIST will have it closer to the required amount.  So in that respect you could say EIST is far superior.


----------



## Mussels (May 25, 2008)

yeah they basically do the same thing.

Good that larujian got straight to the point.

Also, EIST requires OS support (XP and vista do support it natively) while C1E only requires a 'halt state' which is automatically provided in most/all OS's - C1E more or less doesnt require OS intervention, which is why it only has the one step down (it cant see the CPU usage to do it in steps)


----------



## lemonadesoda (May 25, 2008)

The problem with EIST... is that it is a control feature that requires A UTILITY TO monitor and control it.  This has two implications:

1./ Overhead of running the utility (another .exe or service running in the background)
2./ Lag. Since utilisation needs to be monitored over a time interval... it takes, e.g. 1 second for the utility to say "OK, I'm not busy, lets go into power save mode". That's not really a problem. But the reverse is worse, ie. "OK, I *AM *busy, lets get performance back up".  This lag is AWEFUL if you are activiely using a desktop PC/workstation (although it's quite OK for servers to have this performance profile). In practice, it like driving a car with turbo-lag.

C1E on the other hand is done by the CPU itself. It can go into power saving... and back again... instantaneously. The "lag" is supposed to be non noticable. Therefore C1E is better for Dektops PCs/workstations.

For servers EIST is excellent because it slowly scales back performance (and power utilitsation) when the server gets little demand... and turns the power back up when performance is required. Perfect for 24-7 servers with variable utilisation.


----------



## Mussels (May 25, 2008)

lemonadesoda said:


> The problem with EIST... is that it is a control feature that requires A UTILITY TO monitor and control it.  This has two implications:
> 
> 1./ Overhead of running the utility (another .exe or service running in the background)
> 2./ Lag. Since utilisation needs to be monitored over a time interval... it takes, e.g. 1 second for the utility to say "OK, I'm not busy, lets go into power save mode". That's not really a problem. But the reverse is worse, ie. "OK, I *AM *busy, lets get performance back up".  This lag is AWEFUL if you are activiely using a desktop PC/workstation (although it's quite OK for servers to have this performance profile). In practice, it like driving a car with turbo-lag.
> ...



EIST is done the same, and its in nanoseconds. there is no lag due to it... its on by default on every dell system or OEM rig out there, and even 99% of enthusiast hardware (well, INTEL hardware )


----------



## Oliver_FF (May 25, 2008)

Mussels said:


> EIST is done the same, and its in nanoseconds. there is no lag due to it... its on by default on every dell system or OEM rig out there, and even 99% of enthusiast hardware (well, INTEL hardware )



I bet it's also the first thing people turn off


----------



## Mussels (May 25, 2008)

Oliver_FF said:


> I bet it's also the first thing people turn off



actually i've been seeing lots of people here on TPU lately saying they dont, and they love how it saves power/heat even when OC'd.

I always disable it, but its surprising how many people use it.


----------

