Q: Slow USB-speed on iMAC 2011

Hi, My USB-speed is not greater than 6-8 MB/s (measured with Blackmagic ). I have tried 3 different USB-memorys and they are all USB 2.0, so i should get colse to 480MB/s but i´m far from it. Anyone know why ?

BTW i´m using osx 10.8.2

/ Poti

iMac, OS X Mountain Lion (10.8.2), Slow USB-speed

Posted on Jan 9, 2013 11:26 AM

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Q: Slow USB-speed on iMAC 2011

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by macjack,

macjack Jan 9, 2013 12:19 PM in response to Potifar
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Mac OS X

Jan 9, 2013 12:19 PM in response to Potifar

http://www.techrepublic.com/blog/10things/10-things-you-should-know-about-usb-20 -and-30/1265
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by mhadjar,

mhadjar Jan 9, 2013 12:26 PM in response to Potifar
Level 2 (190 points)

Jan 9, 2013 12:26 PM in response to Potifar

USB 2.0 is 480Mb/s not MB/s. So that translates to 60MB/s (8 bits per Byte)

However, with overhead processes, you might see 35-40MB/s realistically.
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by Potifar,

Potifar Jan 9, 2013 2:40 PM in response to mhadjar
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Jan 9, 2013 2:40 PM in response to mhadjar

Thanks for your reply, off course you are right, the theoretical max speed should be 60MB/s. so lets say that practical speed should be 35 to 40 MB/s , my USB is still very slow having 1/4 of realistic speed. My old laptop PC with USB 2.0 is close to 3times as fast (measuring time ,transferring a 2GB movie to same USBsticks ) .
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by mhadjar,

mhadjar Jan 9, 2013 3:13 PM in response to Potifar
Level 2 (190 points)

Jan 9, 2013 3:13 PM in response to Potifar

Are the USB sticks formatted in FAT when using the Mac to transfer files to?
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by Potifar,

Potifar Jan 9, 2013 3:17 PM in response to mhadjar
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Jan 9, 2013 3:17 PM in response to mhadjar

Yes, fat32, but I did a test and formatted the USB to hfs format, but it didn't change the speed.
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by David M Brewer,

David M Brewer Jan 9, 2013 5:46 PM in response to Potifar
Level 6 (9,419 points)

Video

Jan 9, 2013 5:46 PM in response to Potifar

Here are the transfer speed on a 27" iMac-2011...
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by macjack,

macjack Jan 9, 2013 6:32 PM in response to David M Brewer
Level 9 (55,682 points)

Mac OS X

Jan 9, 2013 6:32 PM in response to David M Brewer
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by Jim from huntsville,

Jim from huntsville Aug 10, 2014 5:14 AM in response to macjack
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Aug 10, 2014 5:14 AM in response to macjack

I have the same problem-- I'm thinking it might be because the internal drive is encrypted.
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Q: Slow USB-speed on iMAC 2011

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by macjack,

by mhadjar,

by Potifar,

by mhadjar,

by Potifar,

by David M Brewer,

by macjack,

by Jim from huntsville,

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