Legacy Mode
This mode is traditionally used to access devices attached to embedded IDE controllers, and it is the mode assumed by many legacy operating systems. Each channel requires two I/O address ranges and an IRQ. These resources are fixed and cannot be changed.
Primary Channel
Command Block: 1F0h - 1F7h
Control Block: 3F6h
IRQ 14
Secondary Channel
Command Block: 170h - 177h
Control Block: 376h
IRQ 15
Native Mode
This mode is traditionally used to access devices attached to add-in cards, and it is not supported by many legacy operating systems. Addresses are assigned by PCI Plug-n-Play BIOS. The IRQ is shared with multiple controllers.
Base Address Registers for the Command and Control Block are found in the PCI Configuration Space:
Offset 10h - Primary Command base address Offset 14h - Primary Control base address Offset 18h - Secondary Command base address Offset 1Ch - Secondary Control base address
Certain third-party, hard-drive-related applications may not function properly with SATA drives in Native Mode because the software assumes the drives are assigned the Legacy Mode resources.
"In Legacy Mode you can only have 4 ATA devices, but in Native Mode you can have up to 6 ATA devices, 4 for P-ATA & 2 for S-ATA. Native mode is only supported by Win XP and Win2K"
Hop this make sense!
