Samsung 840 pro performing relatively slow, why..?

hatebreedgr

Junior Member
May 19, 2013
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I've just installed a Samsung 840 pro 128 gb in addition to the 1tb HDD on my IMac 27'' mid 2011.
Did a speed test and the results were up to 360mb/sec read/write, not the 490-520 mb/sec speeds
that is being advertised. The system works excellent but i think the speeds on the
ssd are fairly slower than expected...
all i did is i enabled the TRIM support through chameleon disk optimizer...
any thoughts..?
 

joshhedge

Senior member
Nov 19, 2011
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I'm not sure if the iMac has a SATA 6Gb/s interface in that model, could be the reason why!

Edit: I am partially correct - Read this http://blog.macsales.com/10050-firmware-update-enables-6gbs-in-2011-imacs

If you installed the drive in the Optical bay then you will be limited by a 3Gb/s connection. I would suggest moving the drives around, to get the maximum performance from the SSD as the HDD won't be limited by a 3Gb/s connection.

TRIM wouldn't effect the drive speed, so don't worry about that.
 
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TheStu

Moderator<br>Mobile Devices & Gadgets
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Sep 15, 2004
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I'm not sure if the iMac has a SATA 6Gb/s interface in that model, could be the reason why!

Edit: I am partially correct - Read this http://blog.macsales.com/10050-firmware-update-enables-6gbs-in-2011-imacs

If you installed the drive in the Optical bay then you will be limited by a 3Gb/s connection. I would suggest moving the drives around, to get the maximum performance from the SSD as the HDD won't be limited by a 3Gb/s connection.

TRIM wouldn't effect the drive speed, so don't worry about that.

There's probably no way to swap the drives as I am pretty sure that the iMac would have been using a 3.5" drive.
 

joshhedge

Senior member
Nov 19, 2011
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There's probably no way to swap the drives as I am pretty sure that the iMac would have been using a 3.5" drive.

Ah, I didn't think of that. Still, the 2.5" SSD could fit if a caddy enclosure was used, right?
 
Feb 25, 2011
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*scowl*

If OP were limited by SATA2/3Gbps, he wouldn't be hitting 360MB/sec. (SATA2 caps at 300 theoretical, ~270 in real world tests with SATA3 drives on a SATA2 controller.)

It's easy enough to verify in System Profiler, anyway. There's no reason the be guessing.

Example:
bgzc07.png


Try a few other benchmarking tools first. Some of the OS X benchmarks suck eggs - either not throwing enough data at the disk, or providing really inconsistent results. Ideally, you'd boot into Windows or Linux and run the same tools everybody else uses.