Monday, December 29, 2014

Today's Obscure USB Question

I have mentioned in the past that my antique would not boot reliably if the 1 TB external drive was plugged into the USB port.  I am having similar problems with a USB mouse and keyboard now with the ThinkPad.  I now suspect the real issue is that all the USB devices are sharing a 10-port USB hub, and the real issue is how long it takes for these devices to respond to both Windows and BIOS autodiscovery.  My guess is that sharing the USB cable from PC to hub, means that the PC sends a broadcast message to all downstream USB devices, and waits for a response, and while it takes many seconds for Windows, that is probably too long for the BIOS.

UPDATE: Direct connection of drives to USB port solves the problem.  I have a 5-port hub as well that I will use for the external drives.

8 comments:

Marc C. said...

You could try going in to the BIOS and move the USB option down in the boot menu or try to disable USB boot option entirely if it is not needed.

Nathan said...

Not really pertaining to this post, but I just read that Jerry Pournelle has had a stroke. He is doing better, but also trying to re-learn to type with Windows 8.

http://www.jerrypournelle.com/chaosmanor/message-from-dr-pournelle/#comments

Clayton Cramer said...

Marc: If I could find out how to get to the BIOS boot sequence controls!

Rick C said...

Usually F2 or Del, even on a laptop, will boot into the BIOS. Sometimes F12 will bring up a "choose boot order for this boot" menu.

Here is a list of options for various Thinkpad lines: http://support.lenovo.com/us/en/documents/ht036045

ザイツェヴ said...

The USB enumeration process is much more involved than anyone would imagine. In particularly, there's no such thing as a "broadcast", but devices that are not yet enumerated will listen to ID 0. Software enables hub ports one by one and sends commands to 0, so that a device on the port could respond. In theory there aren't any timeouts. Still, it takes a bit and the process is fraught with misunderstanding between hubs and host software. Things get even more interesting if so-called "translating hub" is involved.

In any case, try to avoid additional hubs for bulk devices such as network cards, storage, scanners, and the like.

Clayton Cramer said...

Rick C: Thanks, it lists every THINKpAD BUT MINE.

Marc C. said...

Clayton, What is the specific model you have? I'm sure the BIOS entry can be found.

Jim Horn said...

The User Manual includes the details on its page 87. You can find that at:

http://www.lenovo.com/shop/americas/content/user_guides/x140e_ug_en.pdf

Looks like a good little machine. I like the size - that's similar to my 2005 Dell Latitude D400 which I use heavily but its 1.8GHz Dothan Pentium M and 1G of RAM is getting long in the tooth. Time for an upgrade...

Laptops are like telescopes. More power is great but not if it's not with you when you need it.