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The ATA spec section 5.14 says the following concerning the signature returned to the host for a few commands (Initial power up, Execute Device Diagnostic, Device Reset, etc) : If the device does not implement the PACKET command feature set, the signature shall be: Sector Count 01h LBA Low 01h LBA Mid 00h LBA High 00h Device 00h This seems pretty clear to me. However, two of the 6 vendor's SATA drives I am testing with are returning 0xA0 in the Device register in response to an Execute Device Diagnostic command. The rest of the signature matches what I would expect. They both also are returning this same signature (with Device = 0xA0) in the initial FIS sent to the host after the link comes up. Is there some history I'm not aware of that would explain why 0xA0 is sent back in the signature? Is there any explanation for this behavior? Thanks, Guy Kendall
