AMD Radeon Performance Enhanced SSDT

You have to generate a whole new SMBIOS for the system. Just changing the model name would not make any difference. Other than messing with your USB Port config and stopping your iCloud account from working.

I use Corpnewt's GenSMBIOS when generating SMBIOS's for Hack's. Simple to use, just confirm the model, i.e. iMacPro1,1 and then tell the script how many SMBIOS to generate, I usually set it to provide 5 full SMBIOS.

This is the first screen you have to deal with in GenSMBIOS script.

Screenshot 2023-01-18 at 20.53.19.png Select option '3' to Generate SMBIOS

The next screen is where you confirm the Mac Model and number of SMBIOS to generate.

Screenshot 2023-01-18 at 20.55.18.png Model and number

Then the script will generate what you have requested.

Screenshot 2023-01-18 at 20.57.24.png Example of 5 x SMBIOS generated for iMacPro1,1

You would need to copy and paste the SMBIOS data to a TextEdit or similar document for later use. As when you select 'Enter' the SMBIOS will disappear and you will be back to the Main GenSMBIOS menu.

This will include the Serial Number, Board Serial Number/MLB, ROM and SystemUUID. All of which need to match, i.e. from the same SMBIOS. Otherwise Messages, iCloud etc. will not work.

You would then need to go to the Apple Support page to check that the Serial Number from the 1st set wasn't being used by a real Mac.

Copy and paste the Serial Number in to the top box on the page, then enter the check Code in the lower box.

If the Serial number is being used you will see a page that states the Support Coverage date.
However what you want to see is the page shown below, which means the Serial Number is NOT being used by a real Mac system.

Screenshot 2023-01-18 at 21.03.19.png This Negative response, is what we want to see.

The Serial Number etc. from the SMBIOS set can then be used on your system without worrying about iCloud, Messages etc. not working.

You would be advised to undertake the following before changing the SMBIOS data and rebooting your system.
  1. Sign out of your iCloud account. As this will cause less issues.
  2. You would need to make two edits in your USBPorts.kext, changing the XHC name and Model name from iMac18,3 to iMacPro1,1, otherwise your USB configuration won't work.
    • Screenshot 2023-01-18 at 21.08.16.png
    • The Screenshot above is an example of where the two locations where the data has been changed. Without this change your USBPorts.kext/USBMap.kext etc. won't work with the new SMBIOS data.
So no it is not as simple as just changing the Model number.
Hey guys, it‘s enough to change the SMBIOS, the Board-ID and - maybe - the MB serial.

The system serial and system UUID can stay the same. It‘s like the Apple service has changed your mainboard.

Personaly I use a Power Mac serial und change the SMBIOS from time to time between iMacPro1,1 and iMac19,1. I never had problems with my Apple-Id or other Apple services. In my Apple account the system is shown as Power Mac from 2004. :)
did you disable the IGPU
In my Z490, yes. In my Z690 I have an KF without iGPU.
In the Z490 no, in the Z690 yes, I have the boot arg. On both systems I get low scores at fresh boot (only with "pro" SMBIOS, not with iMac20,1)
Did you disable the IGPU Empty/headless framebuffer patch
In my Z490 yes, in my Z690 don't have the device properties

So, yes, everything looks right! But two very different systems and still the same weird behaviour!

@Edhawk would you share your EFI? So I can compare it with my two EFIs for the two systems and see if there's something to notice... even though I carefully checked both and wouldn't know what might affect it! On the Z490 the EFI is super clean and minimalistic, only the bare necessary...and with iMac20,1 all is right, so somehow the iMacPro1,1 affects something! Maybe is just a GB5 bug or something...Just curious to know if those low socre reflect on normal use before and after sleep when they increase.
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Maybe is just a GB5 bug or something...Just curious to know if those low socre reflect on normal use before and after sleep when they increase.

See my other reply to your post.
It's a known issue with Polaris GPU.
Does this works for rx6950xt?