USB3 speed theory vs.practice

Data transfer speeds via USB port are very different. It certainly related on system settings (win7_64bit) as well as file type, USB2/3, etc.
My question is related to USB3 transfer, which should be the fastest, but sometimes it's frustratingly slow. I tried several new USB3 external hdds (WDpassport edge 500GB, Adata HV620_500), various flash memory. At the beginning of the big file transfer (1GB), it sets off in cca90MB/sec, then it slows down to 4KB/s. It's somehow improve? Update drivers, or something? I use both Windows Explorer or Total Commander, it's the same.
Thanks for your advice or tip for acceleration.
Peter

 

USB transfer rates have never lived up to the marketing hype. There are just too many variables.

Understand to start, your USB 3.0 devices must be connected to a USB 3.0 port on your computer. But system performance and amount of RAM affect performance too. For external drives, I prefer either network connections or eSATA just because USB is too finicky.