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I have one question about the AHCI support in current EFI BIOS...

Before when we plug external storage card(Ex. PCie-SATA) and attach the SATA drive, BIOS always invokes the Option ROM on that card to do some initializations and provide UI to config during POST...Then we can choose it as boot device !

My question is: (which case is the correct one ?)

  • (case 1) current EFI BIOS natively support AHCI for this kind of external card (here "natively" means EFI BIOS does NOT invoke the Option ROM and can fully configure this card itself then enable AHCI function...)
  • (case 2) current EFI BIOS just natively support Intel or AMD's AHCI controller ONLY
  • (case 3) current EFI BIOS still invokes the Option ROM(no matter for internal or external controller) to support AHCI feature

Regards,

liaoo
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1 Answers1

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Actually it's a little more complicated than that.

To extend the functionality of the UEFI firmware environment a developer can write UEFI drivers. These might be baked into the firmware or they may be part of an Option ROM, which may or may not also have a legacy bios-supporting blob of code!

I don't think the UEFI spec determines what the firmware environment must or must not support in terms of hardware devices, however, it does provide an interface for UEFI drivers to use. As such, either this could be built into vendors' firmware, or it could exist in the option rom, depending on how they decide to do it.

For more, see the best practises for driver development presentation, which is mainly focused on telling driver developers to follow the UEFI spec, but hints as to driver placement too. Particularly the page on common OpROM combinations.

  • Thanks for your comments. Someone told me the current EFI BIOS will invoke the option rom on external card and did not natively support it. That is, the external card vendor should provide the option rom in legacy or EFI style. – liaoo May 06 '13 at 09:09