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Super LFM Question

Last response: in CPUs
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October 18, 2010 6:50:09 AM

Hello,

My Macbook is a 13" Aluminum (Late 2008) with P8600 2.4Ghz CPU 2GB RAM and 250G HDD. I migrated to Snow Leopard last month, and also decided to install Bootcamp and Windows 7 after more than a year of using it.
On Windows 7 OS, I installed the CPU monitoring widget and CPUZ. I immediately noticed that the lowest Freq that my Macbook can operate is only at 1.5Ghz and VID @1.0V (LFM) even with CPU load is minimal.
I knew it is not normal, because I also installed the same utilities on my wife's laptop. She got a Macbook Pro 13" mid 2010 which has the same spec, P8600 2.4Ghz CPU and 250G HDD only with 4GB RAM. There, SLFM is enabled and it works just fine, CPU is running at 798Mhz @0.875V most of the time when load is minimal. Her laptop also runs a lot cooler than mine.

To double check if the issue is not isolated on Windows, I installed Coolbook App on OSX for both computers. Below is what I got.

Macbook 13" Aluminum late 2008 P8600 2.4Ghz 2GB RAM 250GB HDD
Freq VID
SLFM -- --
LFM 1596Mhz 1.0000V
HFM GV2 1862Mhz 1.0500V
HFM GV1 2128Mhz 1.1000V
HFM 2394Mhz 1.1375V

Macbook Pro 13" Aluminum 2010 P8600 2.4Ghz 4GB RAM 250GB HDD
Freq VID
SLFM 798Mhz 0.8750V
LFM 1596Mhz 1.0000V
HFM GV2 1862Mhz 1.0500V
HFM GV1 2128Mhz 1.1000V
HFM 2394Mhz 1.1375V

Legend:

SLFM - Super Low Freq Mode
LFM - Low Freq Mode
HFM GV - High Freq Mode (Geyserville/Speedstep)
HFM - High Freq Mode

According to our Apple local support, they ran Coolbook on all of Macbook 13" Aluminums late 2008 and Macbook Pro models they have and they got the same results. No SLFM for Macbook late 2008 models, but SLFM is working just fine on Macbook Pro 2010.
I checked the Intel P8600 CPU Datasheet and it was noted that SLFM should always be enabled. Otherwise, it will affect battery life, thermal as well as long term reliability of the CPU.

Does anyone know why SLFM is not enabled on P8600 on Macbook late 2008 model?

More about : super lfm question

October 18, 2010 11:00:44 AM

well I think maybe the drivers (when corrected) or the firmware (update) corrected this thing and disabled it. If you have read other laptops that are cooked but their own batteries the manufacturer update the firmware. Maybe they did it on purpose. The manual is not updated.
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October 18, 2010 12:13:38 PM

dEAne said:
well I think maybe the drivers (when corrected) or the firmware (update) corrected this thing and disabled it. If you have read other laptops that are cooked but their own batteries the manufacturer update the firmware. Maybe they did it on purpose. The manual is not updated.


Are you saying that this could be a Macbook EFI issue? I know that other laptops had similar issues but was fixed after a BIOS update.
I got the latest Macbook EFI installed on my computer. Also, this issue is not isolated on my computer. All Macbooks Aluminum late 2008 are affected by this issue.
But why will Apple disable the Super LFM mode of the CPU on purpose?
It will have detrimental effects to the Battery life performance as well as thermal of the CPU. It will actually shorten the life span CPU and will result to reliability issues of the computer in the long run.

How could I get support from Apple? I'm frustrated with the answer that our local Apple support has given me. It seems that they don't know and understand the issue at all.
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