ShhMBP whine workaround?

Question

Has anyone here tried to use the kext called "ShhMBP" to deal with the whine problem on their macbooks until apple does something about it?
ShhMBP is a kernal extension that keeps the processor from entering C4 state which appears to be when the CPU begins to emit the high-pitched whine.
This topic from the Macbook Pro support forum is where it was posted. The download, along with the code, can be found at the link below.
http://discussions.apple.com/thread.jspa?messageID=2654203&#2654203
Check all the way at the bottom of the thread. The code was posted by a user named cbhense. Could someone with some code writing experience glance at the code and tell me whether or not it looks safe to use. Apparently, people using it with the macbook pro are expierencing good results, at the expense of approx 30 mins. of battery life.
I gave it a try and my whine dissapeared, but immediately deleted it because I wanted to check here to see what other people thought of it first. The temps on my machine went up by about 1-2 degrees C at idle with the kext installed.
Has anyone else had any success with this?
Thanks.
White Macbook 1.83GHz   Mac OS X (10.4.6)  

Answer 1

Below is the post in question found at the link above. Any insight on the code or experience with ShhMBP would be greatly appreciated.
-Robb-
Hello Everybody,
as some of the previous posters have noted the Mac Books whine when the processor enters the enhanced sleep mode or C4 state.
The Intel Manual on the 945 chipset specifies that you can disable C4 by entering 10 on bits 1 and 0 at offset 0xf10 in MMR space.
The address of MMR space is found at offset 44h of PCI Device 0 (Host Bridge).
Here's what I did:
Download CHUD tools from Apple, start Reggie.
Go to the Host PCI Bridge and read whats at offsett 0x44.
On my machine I get 0xfed14001.
Go to PhysMem and read 32 bits at 0xfed14f10.
At my machine I get 0x40010.
If you set bit 30 to 1 the whine stops immediately.
You have to start Reggie as root in order to do that.
On my Mac Book the battery run time with 100% charged and an idle desktop drops from around 4h to about 3h 30min.
The Processor temperature rises from about 50 degree to 60 degree.
You have to decide yourself if you want to pay that price in order to stop the Whining.
For me it's ok. I also think it's better than the other methods discussed in this forum.
When the Mac Books resumes from sleep tha bit is set again to 0. So I had to implement a way to set it permanently or to set it again after sleep and on boot.
What I finally did was to write a kernel extension (using XCODE) that sets that bit every second.
The kernel extension I load as a Startup Item in /Library/StartupItems
Here's the source of the kernel extension:
#include <IOKit/IOLib.h>
int stop;
UInt8 data_org;
// Intel Manual on 945 Chipset, page 81, states that
// the offset for MMR space is at offset 44h of PCI Device 0 (Host Bridge)
// Here we read 0xfed14001
// It further states, page 186, that in MMR at offset 0xf10
// we can find a 32 bit value of which bits 1 and 0 control the Enhanced Power Management Mode of the Core Duo Processor:
// 00: All functions allowed
// 01: Disable C3 and C4
// 10: Disable C4
// The default value is 00
// This whole code is about setting this to 10
// Because after wake up from sleep it is set back to 00 we
// have a kernel thread which set to 10 every second
IOPhysicalAddress address = 0xfed14f10;
void qmb_control(){
UInt8 data;
data_org = IOMappedRead8(address);
data = data_org | 0x2;
stop = 0;
while (stop == 0)
IOMappedWrite8(address,data);
delay(1000000);
kernreturnt qmb_start (kmodinfot * ki, void * d) {
IOCreateThread(qmb_control,NULL);
printf("KEXT has loaded!\n");
return KERN_SUCCESS;
kernreturnt qmb_stop (kmodinfot * ki, void * d) {
// Before we can unload this Kernel Extension we have to signal qmb_control to exit.
// If we unload while qmb_control is still running the wake up timer of the loop
// will cause a kernel panic
stop = 1;
delay(2000000);
IOMappedWrite8(address,data_org);
printf("KEXT has unloaded!\n");
return KERN_SUCCESS;
}