mid-2012 MacBook Pro 480GB install low write speed


I installed a 480GB Ultra II SSD today on my mid-2012 Mac Book Pro. It’s running Yosemite with Trim disabled. BlackMagic and Disk Sensei show read speeds in line with the SanDisk quoted at 542MB/s. Write speed seems lacking somewhat at 214MB/s. The SATA link speed is 6GB/s, as is the Negotiated link speed. The SSD is installed into the HDD bay.

The disc is only 30% full and the drive was only installed today so I don’t think the lack of Trim is an issue.

Anyone got any ideas why the write speed should be so low?

Many thanks



the speed of the drive is also related on the hardware you are using with the ssd. so you can do an google search on the hardware that has the mac mid 2012 to see if it has general issues with ssds and the speed of them is very slow.

also to make sure the issue is not hardware related you can test the ssd with another computer that has a sata 3 port to see the speed difference there.

Yosemite OS X 10.10.4 now supports trim on third party SSDs.

Not having Trim turned may well be the cause. 30% full is not necessarily an indication of the available free space of the SSD.

I have a Mid 2009 MacBook Pro with a 240GB SanDisk Ultra II. I just upgraded form Marvericks with Chameleon to Yosemite OS X 10.10.4 and then ran the trimforce command from the terminal window to turn Trim on.

It worked first time, given it is only Sata II, it is still much better than a HDD.

got EXACT the same problem (and EXACT the same Macbook Pro!)

DEFINETLY not hardware problem - as I’ve installed Windows 8.1 on it and… got full write speed :confused:

 anyway - here is SOLUTION

run ‘Terminal’ type - “sudo trimforce enable” - just ‘y’ and ‘y’ and automatic restart - and… it is better - but NOT perfect