Understanding UEFI. Please educate me!

[stuppy_]

Hi

Please forgive this long post. I'm someone who likes to understand why things do what they do, so anyone who can answer any of my questions would be greatly appreciated.  Please don't think that I am someone who is too lazy to read things and educate myself; I read a lot of websites and forums to try and educate myself.  I am often however finding myself still feeling like I have not understood things properly.

 

Up until a few days ago I had only used Chameleon as a boot loader, along with a DSDT someone patched for me which helped me fix my 9800GTX+.  I then used the beast to install some extra kexts (Atheros & Intel network, Marvell SATA controller, AppleHDA for ALC898 etc).  It has been a pretty stable and reliable system.  Even sleep and speedstepping works!.  Since upgrading to Yosemite, however, iMessages didn't work.  While iMessages not working isn't a huge deal to me, it seemed apparent from reading around that Clover was the bootloader of the future.  So it seemed like a good idea to give it a go. 

 

So I installed Clover, and after a few hours of messing, I managed to get booted to the desktop with most things working.  Using toleda's cloverALC patches, I was able to get audio working and my 9800GTX+ worked with just nVidia Inject in Clover Config. I didn't need my old DSDT file at all!  Sleep seems to work, after disabling an option in the BIOS called CPU PLL if I recall correctly. 

 

 

Obviously I understand some rudimentary basics about how it all works, but there are some aspects of this UEFI thing that I don't understand. 

 

From what I have read, UEFI is a replacement of BIOS.  I know that UEFI can read partitions on hard drives whereas BIOS can only see physical drives themselves.  But what is the advantage of this?  Also, what are the other main advantages of UEFI for Hackintosh builds?

 

When I have been researching, I have come across the term CSM a lot and how disabling it allows faster boot times.  When I tried disabling CSM in my BIOS, I had no screen output from either the 9800GTX+ or the onboard Intel graphics.  I had to remove my 9800 in order to regain output through the Intel graphics. 

 

My working understanding, and please correct me if I am wrong, is it allows a computer to boot with both UEFI and non-UEFI (legacy I believe is the term) devices to function together.  For example, in this video, this guys computer boots like a real Mac: 

 

 

https://www.youtube.com/watch?v=J2ZgC5w5kqM

 

 

It appears to bypass the BIOS completely.  Would he have CSM disabled?  And does this type of booting only work if your graphics card has a UEFI BIOS?  I have seen the term 'GoP' relating to graphics cards, but I am not sure what it means.  How difficult is it to get a hack build to boot like this video?

 

Regarding UEFI and Legacy; So at moment when I boot my computer up and I press F12 to get the boot device selection menu, I get a list of all my attached drives.  I get all of them with 'UEFI' prefixed, and then the same drives prefixed with 'P0', 'P1','P2' etc.  I never really understood what these prefixes meant, and even when using Chameleon, if I selected my boot drive with the UEFI prefix, it booted fine. 

 

Since installing Clover to my boot SSD however, I have a duplicate in the boot menu (i.e. UEFI: Samsung SSD shows twice, as well as the legacy 'P1:' entry.  I also noticed some settings in the BIOS under the CSM on/off switch that had labels such as 'Boot Mode Selection', 'PXE Boot Option Control' and 'Storage Boot Option Control'; and these had selectable options such as UEFI only, Legacy only, UEFI first, Legacy first.  I know the PXE one relates to network booting, but the Boot Mode Selection and Storage Boot Option Control, what effect do these have?  One thing I did notice when I set these to Legacy first or Legacy only, I still had the UEFI: Samsung SSD option in the boot selection menu.  Why would this appear if I had set these options to Legacy only?

 

So I am a little confused at the moment as to how I am booting my computer using Clover. Am I booting in UEFI? Or am I booting in some kind of UEFI/Legacy hybrid mode?  Other than faster booting times (as seen in the video above), what other advantages does that guy have that I don't currently have, or am I just missing out on the fast boot time?

 

I really hope some of you take the time to read all of this. I hope I have made sense and I am sure for those willing to educate me, I will have more questions.

Thank you and much appreciated for any help.

Edited October 25, 2014 by stuppy_

[stuppy_]

I have re-written this post to try and condense and make a bit more sense of what I am trying to ask.  Hopefully it works 

[VirusX]

since I have a BIOS only motherboard from 2009, I can't help you with questions regarding UEFI. But I think this might be the wrong subforum for those questions. Also maybe try a different topic title. Good luck!