Help getting a SATA III SSD to run at full speed

First lets correct some impression.
1) ATTO. Most used benchmark by manuf. Reason Yield impressive Numbers. However ATTO was Developed for HDDs. It uses highly compressable data which is NOT real World. Also favors the SF22xx controller based Sata III SSDs (ie most 120 gig sata III SSDs use the SF coontroller). Most 128gig SSD use a different Controller such as the marvel and smasung.
2) Sequencial performance is what is also emphasized, again BS. Sequencial read/writes are the LEAST important parameters for a OS + Program drive. It is the Random 4 K read / writes that are important. 4 K Random Numbers are much lower than Sequencial numbers so you can see why Seq are what manuf favor.

Down to real world.
I'm guessing you have the Old intel MB with Intel Sata II and Marvel Sata III ports. If so use the Intel Sata II Ports, and the latest intel RST driver.
Again a little common sense:
.. Sata III should be twice as fast as Sata II for a SATA III SSD. FALSE. the W is 2x. But if you look at the performance of a Sata III SSD while the Sequencial performance exceeds SATA II, the 4 K Random Does NOT.
.. Yes you will take a "Small" performance Hit in real world Day-to-day Usage , it is NOT as much as implied.
.. The agility III, a low end SATA III SSD that uses ASYNC NAND cells Runs NO Better on SATA III than when on SATA II - Was in a published review plus I verified on my systems as I have 2 x 120 gig Agility IIIs - AS SSD scores are almost Identical

** Do make sure you MBs are running the Latest Bios Rev, and that the SSDs are on the latest firmware ver.

PSS - Always helps in questions like this (dealing with SSDs) if you state the MB make/model, and the SSD make/model.

Hi there,

Thanks. Motherboard = Intel DP43TF

I was comparing ATTO like for like with other YouTube videos and reviews of the same SSD (Vertex 4). Other people are able to get over 500MB/s while I only get just under 300MB/s therefore I suspect this Marvel port thingy is the issue.

Can this be solved with a SATA card? Note this mobo only has PCI-E 1x slots  

Thanks.

Re the controller, the Agility 4 and Vertex 4 uses OCZ's own Indilinx Everest 2 controller. This has much better algorithms thus it exposes the full 128GB capacity to the user. I believe SF controllers reserve those additional space for garbage collection.

To achieve full SATA III performance from an add-on/plug-in SATA III controller card you need to know the following:
1. An available PCI-e version 2.0 x4 slot (or x8 or x16) will provide enough bandwidth for maximum or near-maximum SATA III speed.
PCI-e version 1.0 x4 slot has limited bandwidth and speed.
PCI-e version 2.0 x1 slot also has limited bandwidth.
Your motherboard doesn't have a PCI-e version 2.0 x4 slot. The only PCI-e version 2.0 slot you have is the x16 slot for a graphics card. So, you can have either a wide bandwidth/full-speed SATA III controller card OR you can have a high performance graphics/video card, BUT NOT BOTH.
2. The SATA III add-on/plug-in card must be a PCI-e version 2.0 x4 interface (or x8 or x16).
A PCI-e version 2.0 x1 SATA III controller card has limited bandwidth and speed. This is because the x1 cards have only 1 PCI-e "lane".
An x4 card has 2 "lanes", hence enough bandwidth to handle one or two SATA III SSDs at or near full speed.
An x4 card can plug into an x4 slot or x8 slot or x16 slot.

Afterthought:
I have a Sandisk Extreme SATA III 240GB SSD. My Socket 1366 (X-58 chipset) motherboard only has SATA II ports but also has several PCI-e version 2.0 slots. I connected a Highpoint 620 series SATA III controller card (cost about $22). It's an x1 type (limited bandwidth). ATTO benchmark speeds were measured. Read speed increased, but write speed decreased. Here are the results, with Highpoint 620 speeds shown first: Read (380 / 284) Write (219 / 264).

However, the 4K performance (small files) is arguably more important. Here, the Highpoint 620 SATA III add-on card showed significant improvement for both Read and Write speeds compared to the motherboard SATA II ports. CrystalDiskMark 4K-random Read/Write speeds: Read (37 / 22) Write (87 / 61). I would argue that this level of improvement is worthwhile even though the Sequential Read/Write performance falls well below the Sandisk SSD's maximum ability.

Unfortunately, in your case, you must either use your version 2.0 x16 slot or buy a new motherboard .... in which case you don't need an add-on card !