WD MyPassport 4to : Too Slow!

Hi,

I have 2 WD MyPassPort. One 3to, the other 4to.
The 3to works fine, I mean as expected.
The 4to works but is very slow (under 30Mb/s).

My Passport are connected directly to my iMac.
I have also tried to switch both cables with no success

4to ref is
WDBYFT0040BRD-0A 0318B R/N:D8B EABEGA
Firmware : 4.004

Hi tabasko,

You should check the performance of 4TB My Passport after formatting the drive. If already checked and issue persists again, recommend to use WD Drive Utility to check the health of drive.