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Since upgrading to the Mac Pro 2019, all my card readers where very slow, only getting 10-20% of the speed they should get.
It's a LEXAR 3.0 USB card reader, Lexar XQD card reader and a RED minimag card reader.
I replaced the cable for the RED (USB Type-C to Type-A 3.1), and now my speeds went up from 20MB/s to 300MB/s. Should I buy new cables for the Lexar readers (USB 3.1 cables) or is it a OSX problem or do I need a driver update?
Mac Pro
When you plug in with cable that is only USB-2, you limit your maximum transfer speeds to USB-2 speeds. These cables have only the four obvious conductors opposite the plastic alignment plug.
USB-3 cables add an additional Five conductors, and add speed by going double-rail (push-pull or balanced drivers and receivers) and in some cases double-rail (two pathways). They can run MUCH faster this way. The additional conductors are deeper inside the connectors on both sides, and a frequent (but not 100 percent) convention is that the plastic plugs are Blue in color. Apple does not color their plugs blue.
Problems can occur on the Mac if the first device seen since startup was a USB-2 device. In this case, the bus can get "stuck" at USB-2 speeds. It will stay this way until you do an SMC Reset, or power down and startup again later.
menu > about this Mac > (system report) > USB ...
Check carefully for whether your Mac thinks this Bus is a USB-2 Bus, If so, it may be "stuck".
Hi Grant, these are USB 3 cables I am using, still slow speeds, all blue colored.
Thanks Grant, I'll give it a shot!
Slow USB speeds with card readers.
