GA-EX58-UD4P - Processor C-states do not work while overclocking?

[miccos]

Hi!

I am posting this because I have found out that it seems that the advanced C-states somehow get disabled when overclocking.

It is mentioned in several reviews (e.g. here) that with Gigabyte EX58 boards "all Intel processor power-saving technologies are up and running in idle mode" when the processor voltage is kept at Normal setting and only BCLK is raised to accomplish the overclock. In my experience, not all power-saving technologies work when overclocking.

I have now done some experiments with the following configuration

- GA-EX58-UD4P with F8 bios
- Intel Core i7 920
- 12 GB (6x2GB) of 1333 MHz DDR3 memory
- Windows Vista x64 SP2

- Both C3/C6/C7 State Support and CPU EIST Function are ENABLED.
- Tried both disabling and enablind the CPU Enhanced Halt (C1E), but left it disabled because it causes random audible "squeeks" probably due to a "noisy coil" when enabled.

When the BCLK is left to its nominal value (Base Clock(BCLK) Control DISABLED) and the CPU Vcore is at AUTO or NORMAL, the C states work properly. However, when I overclock, only the C1 state remains in use. The overclock is made by leaving all other BIOS settings to AUTO, but BCLK is raised to 167 MHz and processor voltage is set to NORMAL.

I have verified this C-state problem by using the Performance monitor to gather information about C-state usage. Brief guide:

- Right click My Computer and select Manage
- Open: Reliability and Performance -> Monitoring Tools -> Performance Monitor
- Add monitors (by pressing the + sign): Under Processor, select % C1 time, % C2 time, and % C3 time.
- Change graph type to Histogram or Report

Without overclock I get significant amounts of advanced C-states when idling, but with BCLK change only C1 is in use.

Has anyone other experienced this problem? Are there any solutions to keep the advanced C-states in use other than not overclocking?

EDIT: Here are some links that explain these C-states and their role in power savings:

Intel Core i7 datasheet (especially on page 84 and onwards):
http://download.intel.com/design/pro...hts/320834.pdf

An article on C-states:
http://www.hardwaresecrets.com/article/611/1

[demonsavatar]

I can confirm this on my EX58-UD4P as well with Bios F9a and Vista64 SP2.

When I have my BCLK control DISABLED, I get primarily C3 state usage. However when I have my BCLK adjusted, it only goes to C1 while idle.

I did a power comparison with a watt-meter to see how much the higher C-States saved at stock settings in this thread: Power saving i7 overclocking - QPI and CPU PLL voltage scaling

Enabling C1 saved about 20W at idle. At least with the "NORMAL" voltage setting for the CPU VCore, the CPU voltage and multiplier are lowered considerably while idle in C1. Higher C-States working could save another 10W, which isn't that significant, but I would like it to work.

Perhaps a BIOS fix is necessary?

[demonsavatar]

Same problem in Windows 7 64-bit. Maybe we can get some 32-bit user to check this, or someone running Linux (I dunno how to check this in Linux though) to see if this is hardware/software. I am guessing its hardware/BIOS related.

[frag85]

just registered to say its the same here. i was wondering why after 4 hours the power saved was only a couple watts. i just figured the advanced power saving features were only available below certain speeds (similar to the memory performance features on my old Asus P4P800).

[miccos]

It would seem that other people are experiencing the same problem. Has anyone tested the existence of the issue with a F9c beta bios and/or some Linux distribution?

I wonder whether this is a BIOS issue or a CPU design restriction... Does someone know if the C-states work while overclocking with some other motherboard manufacturer/model?

[demonsavatar]

Yeah I haven't gotten any update on this. I haven't had the time to punch in F9c yet, but once I do this will be on the list of things to check.