SSD SATA II vs. SATA III

Sata 2 drives on a Sata 3 bus will operate at Sata 2 speeds.

mudbucker wrote:

...I have read that if I use a SATA III drive instead, my Mac will treat it as a slower SATA I drive rather than SATA II. Is this true?

I'm asking because most drives today are SATA III, although OWC still sells SATA II drives. These are more expensive per GB than SATA II, though...an OWC 960GB is almost $700 while other brands offer SATA III drives in the 1TB range for under $500...

An SATA III SSD will recognize an SATA II bus and step down to SATA II performance.

The OWC 960 GB SSD is actually two 480 GB SSD's in a RAID configuration that gives 960 GB. As such, it can't support TRIM (though that's problematical anyway once you upgrade to Yosemite), which is a good thing for SSD's in general.

Some SATA III (6Gb/s) drives will in fact revert to SATA I (1.5Gb/s) speeds in some Macs rather than falling back to SATA II (3Gb/s) as it should. One example of this is the OWC 6G SSD. The following is taken from their web page on this (found here - http://eshop.macsales.com/item/OWC/DDMBS6E240/ ):

"

Special note for specific 2009 iMacs, 2008-2010 MacBooks, 2008-2009 MacBook Pros & 2009 Mac mini.

...

While a 6G SSD does function, it will only do so at SATA Revision 1.0 (1.5Gb/s, 150MB/s) speeds rather that the SATA Revision 2.0 (3.0Gb/s 300MB/s) speed the computer can deliver.

"

If you have a computer that only has SATA II, then you may have better luck getting a drive that only supports that speed and no higher. I followed OWC's advice when buying an SSD for my Macbook Pro 5,3 (mid-2009 15") and purchased the OWC 3G SSD. Connects at 3G speeds in both the main HD bay and in the optical bay.

If you are using (a) the OWC data doubler and (b) one specific OWC 240G drive in conjunction with (c) one of a small selection of older Macs you may have the problem.

What is the maximum transfer rate of the drive? is it higher, or lower than 1.5Gb/s

Some SATA III (6Gb/s) drives will in fact revert to SATA I (1.5Gb/s) speeds in some Macs rather than falling back to SATA II (3Gb/s) as it should.

You mention "some" drives, what are they? (other than one older OWC and a data doubler)

The OWC web page sadly refers to all sizes of 6G and Extreme Pro 6G drives from OWC either with or without the data doubler,. See this 6G extreme page:http://eshop.macsales.com/item/OWC/SSD7P6G480/ . You can click on the others to verify this information. I just happened to have the data doubler page bookmarked. It would seem to me that for a Macbook Pro 5,5, the specific machine asked about in this thread, one would do best by purchasing a 3G OWC drive rather than one of the 6G drives. For other makers of SSD, there may be some that also exhibit this behavior, so a good return policy would seems to be the order of the day. Hope this helps.