You can read more about TweakTown's Storage Product Testing Workstation and the procedures followed to test products in this article.
In order to fully utilize SATA III you need a system with native SATA III support. P67, Z68 and X79 systems are preferred, but AMD has made advances in their newer SATA III systems as well. Older X58 systems with Marvell based SATA III ports do not deliver the same high levels of performance, so we recommend newer systems when available.
ATTO Baseline Performance
Version and / or Patch Used: 2.34
ATTO is used by many disk manufacturers to determine the read and write speeds that will be presented to customers.
OCZ Technology Vertex 4 256GB
OCZ Technology Vertex 4 512GB
Looking at the two charts we see that there isn't much of a difference when it comes to the read speed between the 256GB and 512GB Vertex 4. The write speed differences are quite large though, going from around 370MB/s (peak) on the 256GB model to 460MB/s on the 512GB capacity size.
OCZ's marketing numbers were very close to what we achieved in our test.