Ever since downgrading from Lion to Snow Leopard I have started experiencing problems concerning the EFI Firmware on my Early 2011 Macbook Pro. The startup bong is uncontrollable, blue screen when switching graphics cards and a change in resolution when logging out.
So I ask... Does upgrading Snow Leopard to Lion also upgrade or change the macbook pro's firmware?
MacBook Pro, Mac OS X (10.6.8), Early 2011 model.
No.
And, what do you mean by, "downgrading" to Snow Leopard, as that is not technically possible without reformatting the drive and reinstalling Snow Leopard?
No.
And, what do you mean by, "downgrading" to Snow Leopard, as that is not technically possible without reformatting the drive and reinstalling Snow Leopard?
I did it without reformatting the drive. I just made a new partition.
I am sure Snow Leopard and Lion need the same hard drive formatting.
OK, this is not "downgrade", this is new installation into new partition. Downgrade would mean that you started Snow Leopard and it reverts everything from Lion to Snow Leopard leaving intact all (or majority) installed applications, settings etc.
Lion to Snow Leopard Problems
