I will use in this example ICH7 IO Controller HUB specs and show you how to disable(enable) unused root ports as other...
To apply on other ICHx check the ICHx specs b/c some functions/registers may vary(e.g. ICH7 has only 4 UHCI ports and one EHCI).
The board used in this example is a mITX Intel ATOM board, that has only 1 PCI port.
You may use this guide on mATX or netbooks/notebooks.
I do not recommend using this stuff on full ATX boards, unless you know what you are doing...

So what is the benefit of this?
If you look on Apple ioregs(macmini/iMac or mobile) you will see almost on all root ports that are unused(they are not populated or dosen't get populated on card insertion) are disabled by default in EFI.
On our PC's are not, or worst on some crap BIOS some are not enabled(the right one..)
So what are the benefits other then cosmetic?
Each root port if is not disablet get IRQ's assigned, IRQ's are shared and in some cases conflicts may happen, not to mention that on our BIOS'es PCI IRQ routing table is pure crap on most cases, so to prevent an IRQ storm, here is how you can disable/enable them:

The registers part, see page 299, 7.1.56 FD—Function Disable Register, ICH7 IO Controller HUB:



Now you can easy see what can be disabled/enabled, keep in mind that default value for enable is 0 and for disable is 1.
On my Atom board only first 2 root ports are used 0x001E0000(Also know in Apple DSDT as PCIB) for the PCI slot and 0x001C0000 for internal LAN, root port 3 and 4 are eating resources for nothing, 5 and 6 are disabled by Intel in EFI.

So lets disable RP03 and RP04:
Create a new Method right before _WAK one:



To make sure it will stay disabled after wake, we have to add a call for it on _WAK method:



And finally call it on PCI0 _INI:



That's it.

Enjoy!

Interesting, i'll try it on my desktop (ICH9R).
Thanks.

seems it works, but with some issues. for example if i disable UHCI #2, system doesn't boot and goes to reboot loop.

here's for ICH8

There is a reason why I posted the page of the specs...:



Read first, disable after.

I can't seem to write to anything on IHC7-M/945GME, I have tried the cosmetic sub dev id injections, + some, on the other post as well. Is a global lock possible? I have been searching and cannot find a reason.

So far worked on all my hardware, ICH7, ICH8-M and ICH10R.
Check the registers again with specs in hand.

Hi the King,

I have an ASUS P5Q PRO with ICH10R,
Can you tell me what did you disable on your ICH10R motherboard ?

Regards,
Barnum

Hello there,

I'm trying to use this on ICH9 http://www.intel.com/design/chipsets/datashts/316972.htm

Here's what I have done so far


One thing that I didn't understand: where do the vaules 0xFED1C000 and 0x4000 come from?

Thank you.

Thanks for this great info King. To see how this table looks in another dsdt, have a look at the mbp3,1 dsdt. I will be having a look at it to learns how to properly implement this!

Choose a mac with a matching chipset and you can see the correct code in the correspoding dsdt.

I am starting to realize all these hacks are just putting stuff in that mac dsdt already has!!

Cheers,

LS

Same question. 0xFED1C000 - must be a most-used value. But we must be careful, in some cases it may be different.
Am i right?

I though I was very clear in the first post, if not: READ YOUR BOARD CHIPSET DATASHEET!
Here example from ICH8 one:




In translation:
OperationRegion (FDIS, SystemMemory, RCBA, OffsetLenght)

Do NOT copy/paste code from other DSDT's/examples until you double check if it match your chipset and memory registers!