AHCI is a technology that must be supported by your hardware.
Intel:
ICH6R
ICH7DH & ICH7R
ICH8 (all) and later
ICH6-M and later
NVIDIA:
nForce 520, 560, 520 LE, 610a/i, 710, 720, 730, 740 a/i, 750a, 760i, 780a, Geforce 8x00, 9x00, ION, ION LE.
The following chipsets do not support AHCI:
Intel:
ICH5 (i865/875 chipsets)
ICH5-M
NVIDIA:
nForce 2, 3, 4, 500 (except mentioned above), 650, 680i/a, 750i, 780i, 790i with MCP61 and earlier.
If you have additions and corrections, contact me.
Intel:
ICH6R
ICH7DH & ICH7R
ICH8 (all) and later
ICH6-M and later
NVIDIA:
nForce 520, 560, 520 LE, 610a/i, 710, 720, 730, 740 a/i, 750a, 760i, 780a, Geforce 8x00, 9x00, ION, ION LE.
The following chipsets do not support AHCI:
Intel:
ICH5 (i865/875 chipsets)
ICH5-M
NVIDIA:
nForce 2, 3, 4, 500 (except mentioned above), 650, 680i/a, 750i, 780i, 790i with MCP61 and earlier.
If you have additions and corrections, contact me.