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".
Our testing has shown that a four-drive array will sustain maximum reads and writes of about 200 MB/second in a 64bit, 33MHz PCI slot. An eight-drive array will not provide any additional performance beyond that of a four-drive array in that slot. To get significantly more performance, you need to use a machine with a PCI-X slot.