If I use the 2 USB ports on the front of my case I get a transfer speed of about 11.3MB/s.
If I use the 4 ports at the back of my case(onboard) then I get a transfer speed of about the same.
If I use the 4 ports connected via PCI(not Express) slot I get a tranfer rate of about 4.9MB/s.
The Card connected to the PCI slot is called a Silicon Image Sil 3x12 SATALink Controller Driver.
As far as I know I have the lastest drivers for my motherboard, USB devices and SATAlink controller.
Optimising external Drives and flash drives for performance doesn't make a difference either.
I have no idea why these transfer speeds are so slow and it's very frustrating.
USB 2 is effectively 60MB/S or should be, in reality I get 20-25MB/S tops from USB 2 drives.
Try an express card, return the regular PCI card. If you have an eSata try that, let me know if speeds are true to claims. It maybe a power allocation issue too, but I doubt it. MFGS. just lie about the performances of their boards and/or external devices. USB2 compliant = compatible, not performing at best USB2 speeds.
Don't laugh but my MOBO is so old that it only has one PCIe slot and I use it for my graphics card. So that's not an otpion at this point in time. Don't have an eSATA the card has the port on the inside, it is for an internal drive. My USB tranfer rates were always quicker, now they are slower?
My board says what's a PCI-e slot ? :-)
I think something is draining your power and it maybe the internal card.
Have you thought upgrading PSU ??? How many drives and cards you got in the PC ?
How many rails on power supply and what amps you have on 12v and 5v ?