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Old 05-23-2012, 05:12 PM
Mattalones Mattalones is offline
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Join Date: May 2012
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Default It is not the drive

It's the MacBook Pro, not your drive
I have a stock Mac SSD on my MacBook Pro, and it has the same issue. The problem is simple. There is only one SATA plug on the motherboard, but two things are plugged into it. One goes to the optical drive, the other goes to the SSD. They are basically on a splitter (see image below).



Explanation
On a MacBookPro5,5 like mine, the board supports SATA II on its socket. The splitting allocates an even bandwidth as reflected in the System Report. So, you'll get 1.5 gbps on each drive (viz. half-split of 3 gbps) (see image below). This still lets your SSD go up to 187.5 MB/s. So, the split is not a big deal. Plus, Apple's new EFI Update prevents there from being a strict speed cap at 1.5 gbps (EFI update installed before taking System Profiler screenshot below).



Why it's not a big deal
An SSD almost never has to run past 187.5 MB/s for very long anyway. My estimate is that you'll lose 2 minutes over the course of a year. If not, the time you'd save with a dedicated SATA II cable would still be less time than it took to research and find this answer.

Possible nerdy solution if you really want to try it
As a side note before proposing a solution, the new MacBook Pros still have a split SATA III, which will give you 375 MB/s for the few seconds your drive would need to go between 187.5 MB/s and 375 MB/s. As of now, that's the best a MacBook Pro will do without pulling other things apart.

Now for the proposed solution: Since the negotiated speed is a result of having two drives on one wire, you might get around it by unplugging your optical drive. I haven't tried it but that would eliminate the physical bottle neck. If it didn't fix the problem right away, anything remaining would be purely software-based. If you try it, let me know what happens. I'd be interested.

The optical drive uses nowhere near one-half of a SATA II's bandwidth. People don't even use optical drives much any more. If you don't mind unplugging yours, I'm sure others will appreciate some feedback here as well.

Good luck!

Last edited by Mattalones; 05-23-2012 at 05:30 PM.
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