I did a lot of reading last night on how USB works. I believe I understand the problem now. My new hub has a single transaction translator (TT). This TT provides support for the FS/LS devices. Because there is only a single TT this limits the total FS/LS device bandwidth to 12Mb on my 480Mb hub. If the hub had seven TTs I would have had 84Mb for FS/LS devices and no problems.
I've plugged six FS/LS and one HS device into the hub. Each of these devices states how much bandwidth it requires. When you add these up it is more than a 12Mb channel. Now that I understand this the USB spec should never have allowed 7-port USB 2.0 hubs to be sold with a single TT. But for my device collection it doesn't appear to me that collectively they are actually generating more that 12Mb of traffic. Is the EHCI code smart enough to over commit the reservations requested by the devices and then schedule based on actual use? I'm also confused about how my old 4-port FS hub worked. I had most of the same devices plugged into it and it worked. It appear to be that there shouldn't be any big scheduling differences between a 7-port FS hub and a single TT HS hub. They both have the same problem of fitting into a single FS channel. Can the FS scheduling code be applied to the single TT HS hub case? -- Jon Smirl [EMAIL PROTECTED] ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
