-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Alan Stern wrote: > >>I'm pleasantly surprised that the speed of access is *much* faster than >>on the laptop (on the order of 6x faster on writes). My CPU goes to >>100% while accessing the G3, so it makes sense to me that a much faster >>processor (1.8GHz Opteron vs. 1.0 GHz Athlon) would help. Would you agree? > > No. At high (USB 2.0) speed, I/O transfers generally limited by the > device, not by the CPU or the USB connection. Even though your CPU usage > shows up as 100%, it's not at all clear that the CPU is doing anything > useful at those times.
After further experimentation, I'm no longer convinced that anything is faster on my Opteron vs. the laptop. I was using Konqueror to drag-drop files to the MP3 player, and was gauging the speed based on the Konqueror progress window. After many experiments, the time to copy a large file appeared to approach zero (clearly impossible). I suspect some sort of caching effect since a 'sync' command would typically take several minutes to return to the command prompt. This leads me to ask if there is an application similar to iptraf that can show USB traffic details. > >>Now, I can't reliably access the G3 (or my Epson scanner) when it is >>plugged into the EHCI port, but that is the subject of a future thread. > > What do you mean by "the EHCI port"? Remember, on a high-speed system > each port is generally connected to two types of controller: the EHCI > controller and a companion full/low-speed UHCI or OHCI controller. That's > how your motherboard is set up. > While doing these experiments, I was using the 'usbview' GUI. In my case, usbview lists 1 EHCI controller, 3 UHCI controllers, and 1 OHCI controller. I have 6 physical USB connectors on my system. Usbview lists the device underneath the controller to which it is connected. There are only 2 connectors on my system where devices show up as being connected to the EHCI host controller (I called those EHCI ports). If I plug a USB 2.0 device into an "EHCI port", I expect to see USB 2.0 speeds when accessing that device (taking device limits into account). My scanner and MP3 player support USB 2.0, and this fact is recognized by usbview when I click on each device when it is connected to the EHCI host controller. However, what I have noticed is that neither my scanner nor my MP3 player work reliably when plugged into the EHCI host controller. Small data transfers work OK, but large ones (perhaps > 5 MB) return errors, after which the device is inaccessible until unplugged and plugged in again (not power cycled, but dis/reconnected to USB). These devices work great when plugged into either the OHCI or UHCI controller. Why might this be? What can I do to gather more useful debug information? Thanks! Andy - -- Andy Stewart, Founder Worcester Linux Users' Group Worcester, MA, USA http://www.wlug.org -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.5 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFDF5DmHl0iXDssISsRAk/AAJ4viLc2vyPP4OEyBgOWSYNcTZStPgCdHzqL hGGyxbuyO9pORUNu+Fab7BY= =K9mx -----END PGP SIGNATURE----- ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
