AMD and C1E

All about them.

Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee

Post Reply
petieken
Posts: 20
Joined: Sun Feb 14, 2010 5:32 am
Location: Belgium

AMD and C1E

Post by petieken » Sun Mar 07, 2010 9:54 am

I was fiddling with the bios of my Gigabyte MA770T-UD3 motherboard and noticed C1E setting "Disabled".
I didn't even know AMD supported C1E, I thought this was an Intel thing. I have Cool'n'Quiet enabled, but what difference will it make if I switch C1E to enabled?

hans007
Posts: 80
Joined: Sun Oct 09, 2005 3:37 am

Re: AMD and C1E

Post by hans007 » Fri Mar 12, 2010 7:32 am

petieken wrote:I was fiddling with the bios of my Gigabyte MA770T-UD3 motherboard and noticed C1E setting "Disabled".
I didn't even know AMD supported C1E, I thought this was an Intel thing. I have Cool'n'Quiet enabled, but what difference will it make if I switch C1E to enabled?
it only works on athlon II and phenom II cpus with C3 stepping that is why.

dhanson865
Posts: 2198
Joined: Thu Feb 10, 2005 11:20 am
Location: TN, USA

Post by dhanson865 » Fri Mar 12, 2010 10:43 am

from another post of mine
The C3 stepping runs at a lower stock voltage and handles lower Pstates so the idle power draw is better and surprisingly enough it benchmarks better as the additional pstates are handled at a lower level and allow for faster transitions to/from idle enough so that it affects benchmarks. In the case of the X4 965 it means the difference between 140W and 125W.
http://en.wikipedia.org/wiki/List_of_Phenom_processors

From that list the C3 processors are:

Phenom II X4 910e
Phenom II X4 925 (warning there is a C2 of this as well)
Phenom II X4 945 (C2 also)
Phenom II X4 955 Black Edition (C2 also)
Phenom II X4 965 Black Edition (C2 also)

Phenom II X2 545 (C2 also)
Phenom II X2 550 Black Edition (C2 also)
Phenom II X2 555 Black Edition
Phenom II X2 B53

We also know that there will be additional C3 or C4 stepping CPUs. The X6 models are expected in April 2010. Unknown if the other models will be before, at the same time, or after the release of the X6 models.

The model numbers ending in T include Hardware based C-State Performance Boost (AMD equivalent of Intel Turbo Boost)

Phenom II X6 1035T C4
Phenom II X6 1055T C4 (two different TDPs?)
Phenom II X6 1075T C4

Phenom II X4 960T C4?

Phenom II X3 740 C3?

Phenom II X2 560 C3?

Athlon II X4 640 C?

Athlon II X3 445 C?

Athlon II X2 260 C?

I'm not really sure if the new Athlon II models will be C2 or C3 and I'm guessing on the 740 and 560 above them but it's pretty obvious the T models will be C4.

petieken
Posts: 20
Joined: Sun Feb 14, 2010 5:32 am
Location: Belgium

Post by petieken » Sat Mar 13, 2010 7:33 am

I did some testing with my 905e, apparently it works with C2 stepping too. :D

I didn't touch CnQ during my test, it remained enabled for both C1E options.
When it's enabled my idle power consumption dropped about 10W.

I am running undervolted with CnQ P3-State = 400Mhz @ 0.64V. Without C1E I have 75W at the wall and with C1E it's 65W.
Under full load (Prime95) the difference was only ~3W, no real difference.

bottom
Posts: 8
Joined: Mon Mar 09, 2009 4:53 am
Location: Stampy Town

Post by bottom » Wed Mar 24, 2010 6:08 am

same here:

phenom II 720 be:
(should be C2 stepping)

with C1E enabled
idle powerconsumption
drops about 5-8w

buuuuuut:
on my gigaboard board
this option results in a
badly outofsync system-clock !!!


bottom

dhanson865
Posts: 2198
Joined: Thu Feb 10, 2005 11:20 am
Location: TN, USA

Post by dhanson865 » Wed Mar 24, 2010 10:59 am

I've been enabling C1E on inspiron 546 PCs (AMD 780G chipset) with C2 stepping cpus in the last few days.

I looked at the event viewer on one of these PCs and see a number of application hang errors. I'm disabling C1E on one to see if it fixes the issue. The end user of that PC had reported that the PC as a whole was much faster than the old PC they used but that IE was slow to open tiff files. After disabling C1E it appears to be faster doing that task. I'll have to check back on the event log after a day or so and see if it is a clear night and day switch or if the event log still shows errors.

Edit: I just checked the event log on that PC again and it was complaining about the timeserver around the time of the change but settled down a few minutes after I changed the BIOS C1E setting. I'll check again tomorrow but for now I'm going to turn OFF C1E with the C2 stepping CPUs.

I'll be getting some Optiplex 580 PCs soon and will check on those as well.

greenfrank
Posts: 101
Joined: Sat Jan 17, 2009 2:32 pm
Location: Mexico

Post by greenfrank » Sat Mar 27, 2010 11:25 am

I've just enabled C1E on my undervolted Athlon II x2 240. Power consumption of my rig dropped only 1w idle, from 30-31w to 29-30w. For the moment, no errors or strange behavior.

DonQ
Posts: 112
Joined: Sun Jan 15, 2006 12:52 am
Location: Madison, WI

Post by DonQ » Sat Mar 27, 2010 12:47 pm

greenfrank wrote:I've just enabled C1E on my undervolted Athlon II x2 240. Power consumption of my rig dropped only 1w idle, from 30-31w to 29-30w. For the moment, no errors or strange behavior.
My power consumption at idle went down from around 100W to 84W in Windows AND Linux (proprietary drivers).

Phenom II 810
2x2 GB 1066 RAM
Seasonic X-650
Gigabyte GA-MA770-UD3 rev1
XFX ATI 5850
Claro Halo
Hauppauge HVR-1800
Hitachi 250GB 2.5"
WD 1 TB 5400 RPM
USB card reader that idles at 3 W I think
2 IDE optical drives
1 floppy drive

dhanson865
Posts: 2198
Joined: Thu Feb 10, 2005 11:20 am
Location: TN, USA

Post by dhanson865 » Mon Mar 29, 2010 5:01 am

From a recent Server article on Anandtech
C1E mode can only be entered if all CPUs are idle. In a dual socket system, both CPUs enter C1E or they don’t. C1E mode is entered only after longer periods of inactivity. All cores flush their L1 and L2 caches to the L3-cache. Then all cores are clockgated (C1). Once that happens, the Hyper Transport links are put in a lower power state. This allows the chipset to enter a lower power state as well. Only when all these previous steps are done, both sockets are in C1E. DMA events will make the sockets go out of the C1E state. So C1E probably won't happen much on server systems. The C1E state is only entered if absolutely no processing is happening at all.
It might happen more often on home PCs but those of you using folding at home or downloading torrents all the time it won't matter much.

Post Reply