If I don't set up an smbios.plist, my Snow Leopard installation defaults to iMac8,1 (Chameleon 2.0 default I guess).
I usually use iMac9,1, and for a good reason.
These two Geekbench results were obtained on the exact same installation and hardware configuration - the one with the ~30% higher score is from when I'm using iMac9,1 as model identifier.
Click to view attachment
When using an iMac8,1 smbios.plist, VLC media player uses up to 100% CPU time playing high definition H.264 video - when using iMac9,1 it doesn't pass 68%, playing back the same clip - the difference is on par with the Geekbench result.
Running VoodooMonitor when using iMac8,1 it looks like my CPU is locked at its lowest P-State, which is just below 2GHz.

Of course this should only make such a huge difference on a system with AppleIntelCPUPowerManagement loaded.
For more information see this post by 18seven:
http://www.projectosx.com/forum/index.php?...post&p=2062

Yes its very important. Using the wrong model may also load other model specific kext that will give you issues like random kp's (I have seen this with graphics pm). A better method may be to specifically taylor (legacy method) what kext load for your system.

Thanks for the tip man

Yes, for example when using iMac9,1, the system loads the graphics powermanagement profile for the Nvidia IGP in the iMac.

Luckily it doesn't seem to cause any trouble or performance issues but I thought it would be better to have it load a more appropriate profile. So (as you're saying) I use Master Chief's LegacyAGPM.kext which I've edited so that it uses the thresholds and control method/id 18 (0x12) from the MacPro4,1.
Click to view attachment
I've attached it here if anyone wants to have a look.
It loads from /Extra/Extensions, don't forget to set your video cards device ID in the plist before using it.

/revised, attachment updated 10.03.2010.
Click to view attachment

Is there a thread anywhere that gives advice on what model to use depending upon what your MB and video card are? I'm trying to find the best match for my intel D945GCZ ICH7 Pentium D based system with nVidia 9500 GT (G96).

I've been using MacPro3,1 since my first Hackint0sh install, but only recently found that AGPM.kext contained an entry for my 9500GT card under its MacPro4,1 listing in info.plist. Rather than chancing other incompatibilities I just changed the info.plist key to MacPro3,1 to match it up with my card.

Using "the right model identifier" is not that important if you're using a patched kernel and can't have native speedstepping anyway. OS X matches the Power Management stuff with the model identifier (as you have found out) and not with the CPU, but all that is blocked from happening on a system running a non-vanilla kernel and disabler/NullCPUPM.kext.

Since you're not using the vanilla kernel (Pentium D system) you could (probably!) just use MacPro4,1. Have you tried it?

For your MacPro4,1 smbios.plist:



I don't think there's anything wrong with the way you dealt with it though, it's less work, and less of a gamble than changing the model identifier. Though, rather than editing AppleGPM.kext, you could probably adapt the LegacyAGPM that I attached above to fit your needs, it can load from /Extra/Extensions btw. IMHO this is a more elegant solution than hacking at the original AGPM in /System/Library/Extensions.

Yes that is a much better way to do it. I prefer having the kext in /Extra thanks.