| June 23, 2010 |
8.20.2 Interface Path
The Interface Path field at offset 48 allows software external to a system BIOS to locate mass storage device interface chips. The format of this field shall be dependent on the Host Bus type, offsets 36 through 39 of the result buffer.
Table 23 — Interface Path Definitions (part 1 of 2)
Host Bus Type | Offset | Type | Definition |
ISA | 48 | Word | |
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| 50 | Word | Reserved |
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| 52 | DWord | Reserved |
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PCI | 48 | Byte | PCI bus number. Values 00h through FEh shall represent a valid PCI bus. |
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| Value FFh shall indicate that this field is not used. |
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| 49 | Byte | PCI slot number. Values 00h through FEh shall represent a valid PCI slot. |
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| Value FFh shall indicate that this field is not used. |
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| 50 | Byte | PCI function number. Values 00h through FEh shall represent a valid PCI |
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| function. |
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| Value FFh shall indicate that this field is not used. |
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| 51 | Byte | Channel number. If more than one interface of the same type is accessed |
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| through a single Bus, Slot, Function, then the channel number shall identify |
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| each interface. If there is only one interface, the content of this field shall be |
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| cleared to zero. If there are two interfaces, such as an ATA Primary and |
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| Secondary interface, the primary interface shall be zero, and the secondary |
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| interface shall be one. |
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| Values 00h through FEh shall represent a valid Channel Number. |
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| FFh shall indicate that this field is not used. |
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| If the device is connected to a SATA controller functioning in |
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| emulation mode, this byte shall be FFh. |
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| 52 | DWord | Reserved |
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50 | Working Draft Enhanced Disk Drive - 4 |