Help with USB speeds

[USBpr...@hotmail.com]

When I transfer files to flash drive, I am only seeing speeds of about 8-10 MB/second.

If USB 2 is capable of 60MB/second why the am I only getting 8-10. When the copy first starts, I
have seen 60 MB/second for 5-10 seconds, but then it gradually slows down to 8-10. Seems the
larger the file the slower the transfer.

WIN 7 Pro x64... fwiw.

Thanks in advance.

[Sjouke Burry]

Because of writing speed of flash, which has noting to do with
usb speed.
Read flash is fast,
Write flash is slow(and expensive in terms of flash chip survival).

[Paul]

The interface rate on the cable is 480 megabits/sec. Dividing by 8,
that is 60MB/sec.

USB protocol uses packets. The packets have headers. That wastes
some of the bandwidth. Now your usable rate is 57MB/sec.

Next, comes the packet protocol. There isn't a 100% stream of data packets
in one direction. The protocol is more complicated than that. USB uses
a polled protocol.

The end result, is you see things like hard drives in external USB enclosures,
do stuff at about 30MB/sec. Performance tops out, somewhere in that vicinity.

This is an example of a dual channel USB stick. There are two flash chips and
a controller chip. It is a way of combining the bandwidth of two chips. The
numbers stated here are peak values. After a while, you may see the average
rate being somewhat lower than the manufacturer's stated values. The peak
rates are most likely to be evident when transferring a single big file.
Small file transfers will be considerably slower.

http://www.ocztechnology.com/products/flash_drives/ocz_rally2_turbo_usb_2_0_flash_drive

Try a dual channel stick, and see if you get double what you're currently
seeing. More than one manufacturer should make them. It is pretty hard
to fit more channels than that, without making the device bulky.

Paul

[usbPr...@hotmail.com]

>http://www.ocztechnology.com/products/flash_drives/ocz_rally2_turbo_usb_2_0_flash_drive

> Paul

Hi Paul, as luck would have it I had a Super Talent dual channel stick and yes it does acheive
twice the speed. Accourding to the profram USBDeview:

Data traveler write speed is 6.26 while the Super talent is 13.2. When I plugged it into the
motherboard USB port it actually slowed to 12.6.

I guess I don't get where they can say USB 2.0 has a rate of 480mbs/second. I mean.. under what
circumstance does it even acheive 90% of that?

ANy way thanks for your help.

[Paul]

usbPr...@hotmail.com wrote:

>
> Hi Paul, as luck would have it I had a Super Talent dual channel stick and yes it does acheive
> twice the speed. Accourding to the profram USBDeview:
>
> Data traveler write speed is 6.26 while the Super talent is 13.2. When I plugged it into the
> motherboard USB port it actually slowed to 12.6.
>
> I guess I don't get where they can say USB 2.0 has a rate of 480mbs/second. I mean.. under what
> circumstance does it even acheive 90% of that?
>
> ANy way thanks for your help.
>

I'm unaware of any device transferring faster than about 30MB/sec or so.
I'm still waiting to be impressed :-)

Paul

[david]

On Sun, 03 Jan 2010 00:58:32 +0000, usbProblems rearranged some electrons
to say:

That is the maximum transfer rate of the physical interface. It does not
take into account the protocols involved. FWIW we designed a custom USB
interface to capture high speed serial data from a large number of
devices. Because it was custom, we were able to optimize the transfer
rate by using mostly high speed isochronous block transfers.

[Sam Yosemite]

david <no...@nospam.com> wrote in
news:hhq6cb$211$1...@news.eternal-september.org:

May I ask who "we" is and what rates you acheived?

Thanks,

Sam

[david]

On Sun, 03 Jan 2010 16:29:03 +0000, Sam Yosemite rearranged some electrons
to say:

Sorry, I can't divulge that info. It was done by my company for a
restricted project.