Inconsistent write speed on USB flash drive

I've noticed lately that my USB transfers seemed to be taking longer from the front port in my computer. No idea how long it's been going on, really. I was kind of assuming my front ports were maybe USB 1.1 and the rears were 2.0, but was too lazy to check. (This is a new computer case)

Anyway, today I decided to see if the rear ports were any faster. I took a 16 GB TDK brand USB flash drive and popped it in the front-left port and transferred a single 160 GB file to the drive while timing it, then deleted it and rotated through the other five ports. Here is what I got:

front left....2m56s
front right ...0m44s
back bot left...0m24s
back bot right...0m23s
back top left...0m20s
back top right..0m20s

For giggles, I started to repeat the trials on a few ports and this time:

front left......0m13s
front right ...0m20s
back top left....2m55s

...So my slowest port in the first trial was front left 2 min 56 sec, but the second time it was only 13 seconds! The back top left was the fastest the first time at 20 seconds, but then was nearly 3 minutes the second time.

Running XP Home, SP3, several 1 TB HDDs, Intel P4 Prescott 3.00 GHz, 4 GB ram, D865PERL MB.




I have no idea where to go from here, but I'd like to get to the bottom of this. Any suggestions?
4 answers Last reply
More about inconsistent write speed flash drive
  1. - I know it's a dumb question, but, you are transferring exactly the same data each time?

    - The pc is in exactly the same state each time? - absolutely nothing going on in the background - you may want to repeat a few more times.

    - that's quite a difference in the front left scores! - try repeating this a few more times.

    - depending on the usb port used, a different hardware controller may be getting used (different hardware can easily yield different transfer rates) - again, more repeat testing required.

    - data caching - more repeat testing required to normalise this.
  2. Yes, same exact file. I was just plugging it in, copying and timing, then deleting and moving it to another port. I think I might have had firefox or email open in the background, but I wasn't opening and closing applications.

    I'm going to try again with another USB flash drive, but my computer is tied up analyzing some (actual work) data right now.
  3. It will be interesting to see the results with the other drive. I would also hit any one port with a minimum of 5-10 repetitions.
  4. My apologies for the long delay, but I believe I have solved the problem and wanted to update the thread in case anyone in the future was curious. It appears that the problem was in a setting in my BIOS on the D865PERL motherboard. Under USB 2.0 Legacy Support, I had "Full Speed" selected. I didn't consider that there might be a faster setting than "full speed", but apparently, there was. Setting it to "High Speed" fixed my problem.

    Not sure how I missed it before, but:
    HiSpeed = 480 Mbits/sec
    FullSpeed = 12 Mbits/sec

    I again transferred the same 165 MB file to two different 16 GB USB thumb drives and timed the transfer. I stopped testing after doing the three ports because of the obvious success of changing the setting.

    USB PORT: Trial times for 167 MB file transfer (in seconds)
    Front Left: 15, 12, 14
    Front Right: 13, 14, 14
    Rear Upper Left: 15, 14, 14

    That is MUCH improved!
Ask a new question

Read More

Flash Media USB Flash Storage