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Why Super LFM is not enabled for Macbook 13" late 2008 model?

Last response: in Laptops & Notebooks
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October 18, 2010 6:54:40 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 Macbook late 2008 model with P8600 CPU?
a b à CPUs
a b D Laptop
October 18, 2010 6:45:58 PM

I dont know if anyone but Apple can tell you the reason, but if its not working and the CPU's are the same then its probably a motherboard issue.

I have a P8700 in a Dell and I use SLFM all the time, (manually tuned voltages, I can so 1866Mhz @ 0.875).

There are two possible solutions. I assume Mac's have BIOS/Firmware updates you could try that. If that doesnt work, there is a solution in windows to manually set voltages for specific frequencies, you can use either CPUGenie (Paid for program), or RM Clock (Free, but you need to manually sign and load the 64bit DLL).

EDIT: I dont know if this programs will work on a Mac based PC. (difference in motherboards)
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October 19, 2010 5:37:12 AM

Snipergod87 said:
I dont know if anyone but Apple can tell you the reason, but if its not working and the CPU's are the same then its probably a motherboard issue.

I have a P8700 in a Dell and I use SLFM all the time, (manually tuned voltages, I can so 1866Mhz @ 0.875).

There are two possible solutions. I assume Mac's have BIOS/Firmware updates you could try that. If that doesnt work, there is a solution in windows to manually set voltages for specific frequencies, you can use either CPUGenie (Paid for program), or RM Clock (Free, but you need to manually sign and load the 64bit DLL).

EDIT: I dont know if this programs will work on a Mac based PC. (difference in motherboards)



First of all thank you for replying. I already called Apple technical support here in Asia twice but they can't give me an answer. That's what I was suspecting also. This could be a motherboard or an EFI issue that Apple has to fix.
The problem is, Apple technical support can't give me an answer.
Actually, it seems that they actually, don't know what I'm talking about. Their product is so expensive and yet they give you a good support when you need it.
Any suggestion where I can escalate this question to Apple or what should be my next step?
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