/System/Library/Extensions and /Extra/Extensions both have their own caches.
But if you have 2 or more OS X versions in your Hackintosh, and need especific kexts, you need put your kexts in the corresponding folder. If these folders are not there, just create them And use this value in your config.plist to update the Clover cache - Read more about that here: Inject Kexts and No Caches Note for Clover users: Don't duplicate the kexts, or you use in System/Library/Extensions or in EFI/Clover/kexts/**** Note that on 10.7 Lion systems, the kext cache by default is ignored. Backing up insures that if you mess up, or if something goes awry, you have a recent backup handy to restore the computer to. Backup your Mac with Time Machine before beginning.It is very necessary; whenever you install a new kext, if you don't update the caches it renders the driver ineffective!The user can override this choice by holding down the Option key while the computer boots, which causes EFI to display a screen for choosing the boot volume.Once Boot ROM is finished and an OS X partition has been selected, control passes to the boot loader.