P/SATA compatiblity/native mode

There are actually 3 modes that SATA controllers can operate in:
  • Native mode where no IDE emulation is done and OS uses the SATA controller’s native interface (usually AHCI) as the interface to the hard disk.
  • Native IDE emulation mode where IDE emulation is done and it’s IRQ and base I/O addresses are dynamically assigned by PCI.
  • Compatiblity IDE emulation mode where IDE emulation is done and it’s IRQ and base I/O addresses are fixed at the values dating back to the original IBM PC/AT’s WD1003.

Problem is, these modes are frequently confused, especially because of poor naming.
Most newer motherboard built-in PCI PATA controllers can run in compatiblity or native mode, which is the last two modes above.
Most PCI ATA add-in cards can only run in the first two modes above, as the PCI connector do not support the fixed IRQs needed to run the last mode above without a ISA paddle board.
Older motherboard built-in PCI PATA controllers and all ISA PATA controllers can only run in the last mode above.
On OS support, Win9x, NT 4, and most other older OSes only has built-in support for the last mode above, Win2000 and later and most other newer OSes have built-in support for the last 2 modes above, and Vista and most even newer OSes has built-in support for all three modes.
More on the last two modes above at:
http://www.microsoft.com/whdc/device/storage/Native-modeATA.mspx
http://suif.stanford.edu/~csapuntz/specs/pciide.ps

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