You can check your Macintosh System Profile. When you select the installed eSATA card, the Device ID will show either "0x6081" or "0x5081". The 3 Gigabit/second eSATA cards use the Marvell chip 88SX6081. The 1.5 Gigabit/second eSATA cards use the Marvell chip 88SX5081.
Macintosh bootable volumes are supported on the internal 2-port PCI card (part number TSATA) but are not supported on any of the other SATA cards at this time.
The new 3 Gigabit/second eSATA cards contain a rather large Marvell chip with the string "88SX6081" on it. Previous generation eSATA cards had a Marvell chip labeled "88SX5081". Additionally, you can check your Macintosh System Profile. When you select the installed eSATA card, the Device ID will show either "0x6081" or "0x5081".