USB Devices and restarts

All things being equal your PC should be able to successfully pass through the BIOS controlled BOOT process (without any BOOT hang) with the USB peripheral devices still attached to root Hub ports on the rear or front panel or (more obvious) an internal USB port. Likewise if devices have been compliance tested at several Hub levels (for example attached to Monitor or Keyboard Hubs) during the BIOS controlled BOOT process.

You should never have any problems attaching USB compliant devices after the BOOT phase (excluding USB Keyboard & Mouse devices that should always remain attached). Suggest you read other related USB problems in this Forum, for example my recent reply on this subject.

Not sure if this helps?

Compatibility between BIOS code & USB HID (Human Interface Device) class devices (such as Keyboard, Mouse) is critical during the BIOS controlled BOOT process; incompatibility causes BOOT hangs. Normal compliance testing is at one Hub level & preferably through several hub levels. Think that DELL & its suppliers would have complied with the latter testing level?

The subject gets even more complicated (as expected), information & functionality of any USB device is defined within its group of descriptors (many of them), a bit like all the properties of the USB device. Within the descriptor named USB Configuration Descriptor is a member called wTotalLength that specifies the total length, in bytes, of all data for the configuration.

Some BIOS cannot handle long descriptors such as the USB Configuration Descriptor if the value of wTotalLength is above a certain value. Monitors with integrated Hubs and HID controls tend to contain long descriptors. BOOT hangs will result if BIOS cannot handle a particular long descriptor during BOOT phase. Again I’d think that DELL would have ensured long descriptor devices could be handled by present BIOS versions?

Not withstanding my above technical summary, the problem of why using some USB ports is OK & other ports cause problems remains a mystery (hard wire or contacts problem)?

Finally I understand industry is fast moving toward enable booting from USB devices, in particular use of the USB Mass Storage device class. Not sure if all recommendations, standards etc were resolved by end of 2005 but now find it interesting that diagnostics LED 1 & 4 = Storage Device Configuration or Failure. I tend to buy DELL because they have a reputation of building PCs for the future or emerging technologies, hence my original concern (post date 03:02:2006) about having to change USB Controller factory default setting from ON to No Boot.

Bell Boy,

Many thanks for your detailed reply. I have already disabled/shut off  USB Boot in bios setup and am still having a boot hang problem. As of now I have disconnected all devices and am plugging them in one at a time and restarting each time to see if I can find the one device that is causing the problem.

Is there anyway that you know of to change values for the descriptors you mention in the properties of a device, to see if that change will no longer cause a boot hang, once isolating the device, causing the hang?

Jas

Unfortunately you cannot or shouldn’t (even if you could) change USB descriptors they are complex sub routines.

But what you are doing is correct (trial & error with USB peripherals) you should also try any problem device in another USB port. First try another port on monitor hub, if it still causes BOOT hang you should try connecting to different Root Hub ports as previously suggested. Alternatively you can just plug in your cam after BOOT.

If you have time you should look at peripheral properties in Device Manager USB Controller/Root Hub either when cam is connected after BOOT or before BOOT (if a successful USB root port connection is found). It may give you some clues to what’s going on, for example does the USB cam device appear in a different Controller/Root hub when changing Hubs or Hub ports?

Bell Boy,

Again many thanks. I will press on and try connecting to my second monitor port and see what happens with that. I had not tried that yet. I do know from previous problems, with my MS Fax software, that the Logitech Quickcam also causes a complete system crash with it, whenever I try and send a fax while the cam is connected. If I disconnect it and send a fax all works fine. Of course I have brought this to the attention of Logitech support with no patch no results!!

As you mention of all else fails I can just always reboot with the cam disconnected and then reconnect. I have to disconnect it now if I want to send a fax...

Jas, I will add on to say that a logitech quickcam pro 4000 or a logitech g5 plugged into my LCD's usb hub will cause my xps400 not to post.

Just thought it interesting that logitech devices were killing it for you as well.  I can POST with either device attached to a different usb hub and I can POST with each device directly connected to the back of the computer.  LCD hub hangs on POST though -- but works fine otherwise

Nemisis,

Thanks very much for your post on this issue. Dumb me probably, but I have not tried to move all my usb devices around yet from port to port to see how that would react. I guess because I am one of those old folks that still thinks all of this stuff should work and be tested first, but then I guess that is NOT the real world.

Sooo, I will now see if I move my Logitech to one of the rear ports if that will work or not in either case the Fax or the Boot process.

Can you imagine what the poor folks do that are not at the same level of computer literacy as some of us are!! And I'm sure that my level is far below what some of the guys who post here are at..

The USB ports on a monitor are basically an unpowered USB hub.  You have to take into account account power requirements and bandwith requirements when you start plugging in lots of stuff.  The monitor ports are find for low speed things (keyboards, mouse) or low bandwith things (speakers).  See http://www.usb.org/developers/usbfaq/

If you run out of rear ports, your best bet is a powered USB hub.  They're pretty cheap

just curious but how does the powered unpowered make any difference for high, low, full speed devices?

i can see how you wouldn't want to use power hungry devices with it, but I'm not sure how the other would matter.

i don't think that's what's in play here though -- all my devices seem to run fine once POST has completed on the monitor ports.  fyi my g5 mouse (and presumably the webcam) are both full (not high) speed usb devices

That's the same that happens to me. Once my system has completed bootup, I can plug the cam back in the monitor port and it runs just fine.

Of all my usb devices it is the only one that will not make through a normal startup.

Think davejohn may be highlighting problems when plugging USB 2.0 (Hi-Speed) devices in bus powered ports (100mA/port max), or may be referring to possible electrical surge on Hub port, which can result in Hub turning the port off (hope not). Never tried former or experienced latter but I’m sure Windows XPS SP2 alerts you in either case & makes polite suggestions! He is probably referring to bandwidth limits since data transfer mode for cam device is isochronous therefore requires a guaranteed amount of bandwidth. Again if USB devices are arguing over bandwidth you should get a Windows error message. Oh, forgot to mention it in last post but USB cam devices also contain long descriptors that can cause BIOS handling problems (a buffer size issue).

If not already checked, suggest you go to Control Panel > System > Hardware > Device Manager, expand/open USB & look at properties for USB Host Controllers their Root Hubs & USB peripherals attached you should see all relevant information in Generic USB Hubs (power limits), Controllers (bandwidth used) etc, etc. Should also indicate if there are any conflicts. My 1905FP Monitor Hub shows up as a Self Powered (500mA/port) Generic USB Hub with 4 ports (power comes from mains power supply to monitor).

Finally I’m not sure on DELL specific BIOS control BOOT sequence but I understand POST process is normally an early step in a typical 13 step BOOT sequence with BOOT drive search only a few steps from the end. It may just be a coincidence but if BOOT sequence is linear my BOOT hang USB problem occurred at about 70% sequence complete (as indicated in BOOT progress bar). Hence no POST alerts & just about the step range where BIOS handles PnP devices. Food for thought, not sure?

Again, many thanks. In my case I did a trial and moved the Logitech Cam to a port in the rear then rebooted and no problems, whala, clean no problem boot, but that still leaves the problem that my Logitech also causes which is a system crash when ever I try to use MS Fax with the cam plugged in. So for me I have gone back to connecting the cam up only when I need to use it to the hub port on the monitor. As long as I have it setup that way I can still send faxes when ever I need to and do clean no problem reboots.

Maybe one of these days Logitech will get there act together and produce a fix. This is a known issue with their software..