[SeaBIOS] [PATCHv6 00/16] boot order specification

Sebastian Herbszt herbszt at gmx.de
Thu Dec 2 22:22:03 CET 2010

Gleb Natapov wrote:
> How can we get to EDD info after device is mapped? Looking at Seabios
> implementation it builds EDD table on the fly when int_1348 is called
> and it does it only for internal devices. Can we use "disconnect vector"
> to connect device temporarily get EDD and then disconnect?

>From BIOS Boot Specification 1.01

"6.4.2 Disconnect Vector

Originally, it was thought that the DV would be called by the BIOS if the device's
BCV was called and subsequent booting from the device failed. However, it was later
discovered that current PnP option ROMs are more well behaved by checking during
the BCV call if their device will properly respond to INT 13h calls or not, and simply
not hooking INT 13h if those calls would fail. Because of this, the DV is not called by
a BIOS supporting the BIOS Boot Specification, nor is it necessary to have a valid DV
in the PnP Expansion Header. The DV should be NULL and can't be used for other


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