Note that the speed reported in a SATA II port sound ok and regarding the SATA III port that you are using it depends of the controller and how it is connected on your system the performance that you will get, you can find more information in regards the overall performance of that specific family of Solid State Drives at the following link:
Your mother board may not support PCIe 2.0 speeds, I can't see that on the product page. Given the age of the board, and the single "universal port", that may be the limitation. The riser card may be causing a limitation as well.
Your Rocket card has been reported to really reach full SATA III speeds. How many drives are connected to the Rocket card?
Thanks Parsec, I was hoping you would chime in.
I am currently only running one drive off of it.
So would this pci-e slot be coming from the PCI 1.1 from this chip
on the mother board
Thanks for your comment. Yes, the PCIe 16x lanes are provided by that chipset. PCIe lanes were not provided by the CPU until the Intel Sandy Bridge architecture. The other chipset on your board, the ICH7, provides one PCIe lane which is used by the network chip.
This is an excerpt from the 946 chipset family data sheet:
The (G)MCH contains one 16-lane (x16) PCI Express port intended for an external PCI
Express graphics card. The PCI Express port is compliant to the PCI Express* Base Specification
revision 1.1. The x16 port operates at a frequency of 2.5 Gb/s on each
lane while employing 8b/10b encoding, and supports a maximum theoretical
bandwidth of 40 Gb/s in each direction.
On the 82946GZ the PCI Express interface is multiplexed with the SDVO ports.
Capabilities of the PCI Express Interface include:
One, 16-lane PCI Express port intended for Graphics Attach, compatible to the PCI Express* Base Specification revision 1.1.
PCI Express frequency of 1.25 GHz resulting in 2.5 Gb/s each direction
Raw bit-rate on the data pins of 2.5 Gb/s, resulting in a real bandwidth per pair of
250 MB/s given the 8b/10b encoding used to transmit data across this interface
Maximum theoretical realized bandwidth on the interface of 4 GB/s in each
direction simultaneously, for an aggregate of 8 Gb/s when x16.
The bad news is the speed of the PCIe lane is 2.5 Gb/s (bits, not bytes). The good news is you seem to be using two PCIe lanes in each direction, for a total of 5Gb/s. But that does not provide the full 6Gb/s needed for SATA III speeds.
User reviews of the Rocket card claim it is using only two PCIe lanes, rather than four, as is claimed for the card. I don't know if that is true or not, but it seems you have a four lane connection, but two are used as the input, and two for the output. The connection seems correct, but the limitation is the PCIe 1.1 speed.
Your 350MB/s read speed is typical for a Marvell SATA chipset with a 5Gb/s connection. Nothing can be done about this, unless your BIOS allowed you to increase the clock rate of the PCIe buss, which is unlikely, and would probably create instability, leading to BSODs.
I know it's nice to see 500MB/s sequential read speeds with SSDs, but that alone is not what matters in disk drive performance. The 4K read and write speeds are very important, and if they are less on the Rocket card than the Intel SATA II ports, your real world performance could be better using the SATA II ports. The latency may also be lower on the SATA II ports. Can you set the SATA mode to AHCI on that board? If not, the Rocket card which should support AHCI is the better option.
Can you run the Windows 8 Optimize feature to manually TRIM SSDs with the Rocket card?