Regarding the mid-2009 MacBook Pro (mine is a
5,4), here are the considerations I made in the Samsung 840 thread:
Two 840s (TLC), one in the main bay and one in an Optibay, in a mid-2009 MacBook Pro 5,4 with the 1.7 firmware update, which allows for SATA 2 speeds: and the good news is that it negotiates at 3 Gbps in both bays, also the ex optical one; and also no beachballs, sofar: very good, indeed!
Both SSDs required a firmware update, which worked perfectly with the downloadable ISO CD method, both from the internal optical drive and the same drive moved to the external USB enclosure included with the Optibay: so, the downloadable DOS CD updater works also from a USB connection, which is very good; rather excellent support from Samsung also for (older) Macs, thus.
So, the Samsung 840 (Pro), working perfectly at 3 Gbps also in the optical bay, contradicts what they say about this problem for some older MacBook Pro's on the OWC site:
http://eshop.macsales.com/item/OWC/DDAMBS0GB
... at the end of the page:
2008 MacBook Pro 15" (MacBookPro 5,1; 5,2; 5,3; 5,4; 5,5 and MacBook 5,1)
While a 6G SSD does function in a 2008 MacBook Pro 15" and 13" Macbook, it will only do so at SATA Revision 1.0 (1.5Gb/s) speeds rather that the SATA Revision 2.0 (3.0Gb/s) speed the machine can deliver. Should owners of these machines desire another SSD option, the Mercury Electra™ 3G SSD does run at the full SATA Revision 2.0 (3Gb/s) specification.
The Samsung 840 (Pro) is indeed a 6G drive, but negotiates perfectly at 3G also in the optical bay, at least on the MacBook Pro 5,4 (which is a mid-2009, while on their site they say only 2008 for all those models).
The Optibay that I used is from MCE: apparently, the latest one, with the four lateral screws to support the HD/SSD (and, thus, no top/bottom plate: i.e., transparent at the centre, so to speak...).
Just FYI...