I was wondering: do you have your iGPU HD 630 listed on about this mac>system report>graphics/displays?
I don't.
I am under the impression that the system is not properly identifying the HD 630 (perhaps causing some component of graphics acceleration to be disabled)
Try to run any video with QuickTime and check iGPU usage in
Intel Power Gadget. Even when I play
Sony Camp 4K Demo.mp4, my CPU is idling, and iGPU load is about 40%. So, iGPU is working fine even if it is not presented in Graphics/Displays tab.
Do you have any idea how can I enable it back?
I never hear that iGPU should be available in Graphics/Displays. And that iGPU not working if it isn't there. So check iGPU utilization with Intel Power Gadget. And if system uses it, don't worry about Graphics/Displays tab.
Perhaps I should use system definition iMac18,1 instead of iMac18,3 I am using now?
High chance that you will break something. iMac 18.1 don't have eternal GPU. I experimented with iMac 18.1, and something was wrong. But I don't remember what exactly.
One more thing: when you turn on your computer, what is the behaviour of your Apple loading screen? Mine starts to load the bar, then the monitor goes black for an instant, then my GPU fans spin at full speed for an instant too (like half a second), and then the Apple bar finishes loading, and I can see the operating system screen. Does yours do the same?
I think it depends on GPU. Short fan peak is normal behaviour. My build act like this:
1. BIOS welcome screen (short fan peak, ~60%)
2. CLOVER screen (~30% almost silent)
3. Apple logo without progress bar (~30%)
4. Typical Login screen with wallpaper (FileVault preboot, ~30%)
5. Apple logo with progress bar (~30%)
6. Dark screen (~15%? silent)
7. Apple logo with progress bar (~15%)
8. Desktop (~15%)
I have HD630 listed when I checked Colver > Graphics > Inject Intel, but when I try connect my monitor with HDMI port on my motherboard then I got a glitched not really visible.
I tried this option yearly today and yes, iGPU is visible in Graphics/Displays tab. But, hardware acceleration doesn't work at all!
When I play Sony Camp 4K Demo.mp4, I see 50% CPU load and no iGPU load.