Slow usb 3 speeds 40mb/s ?

Just installed a usb 3.0 i/o card in my PCIe and connected a 3tb WD external drive and am only getting at max 40mb/s transfer speeds.

win7 64bit
8gb ram
e5200 intel 2.5 ghz

any ideas on what to do to get this running optimally are appreciated

Hi Bri,

Thanks for posting!

40 MB/s sounds a little slow, but not too out of the ballpark in terms of a real-world throughput for typical mix of operations to a SATA drive.

Although USB 3.0’s theoretical peak is 10x USB 2.0’s theoretical peak, neither gets the whole way there even in the best case.

And, at least for now with USB 3.0, the bottleneck is usually on the USB 3.0->SATA bridge controller side and to the drive itself.

I know you’re not using our USB 3.0 SATA dock, but on it we use a LucidPort USB300 chipset (…) in “BOT” mode (that is, using the standard Windows USB mass storage drivers), and here’s LucidPorts prior tests on performance in that scenario vs. a different UASP mode that they offer:…

Of course, a typical scenario will be a mix of seq/dyn reads and writes. In the case of hard drives, there are bottlenecks at a number of layers.

Hope that helps in terms of expectations. Sorry USB 3.0 may not be able to deliver as big a jump as you hoped. Let us know if you have any questions!


In the above link they get weak performance form an offering that WD provided, and they got between 128 and 145 MB/s, which is what i was expecting, especially since the throughput on the PCIe 1x that you plug it into has a max 250mb. I knew i wasn’t going to see the 5gps but i thought at least 80mb/s on the low low end especially for a standard thats trying to top eSATA. I just didn’t know if there was a setting that i may have missed, or may need to adjust, in the BIOS, or maybe newer firmware.

Hi Bri - configuration improvements can help, but there are limits.

I couldn’t tell from the Tom’s hardware review how they measured those numbers - could you tell?

We’ve found the biggest difference in USB 3.0 transfer performance to be with the cable/connection to the external drive (lots of USB 3.0 cables out there which generate errors on the line), and then the USB 3.0 SATA controller and firmware. Next biggest factor is the CPU, actually - if any processing causes transfer windows to be missed, you’re giving up throughput. We’ve seen good jumps on faster CPUs.

In terms of firmware and driver at the host controller: the NEC/Renesas μPD720200 is the most common on the market, if from us you’ll have fairly recent firmware and drivers, and none of the recent firmware/driver updates have made large differences in performance that we’ve seen.

You’ll see the roughly the same performance with all the common USB 3.0 add-in cards on the market.

In coming weeks, we’re hoping to do a series of posts on on maximizing USB 3.0 storage throughput where we try to break all this down and get some numbers beside each tweak.

Until then, if you do find any different info or tweaks which help or have any specific questions or requests for us, please let us know.