Baffling USB Ports
I am working on a Alienware Area 51 with Abit AA8XE motherboard running Window XP Home. This computer has 4 USB ports on the back and 4 on the front panel. The customer has a large number of USB devices (11) that I just can’t get to all work at the same time.. The problems do not seem to be specific to which devices I have plugged in, but rather how many are plugged in.
It was all working fine and The problems started with the computer would not boot and would just hang at the first Windows XP screen. I found that by unplugging a USB ZIP drive the problem went away. Then other problems started to crop up like one of the external USB hard drives was not recognized and came up under device manager as an unknown device. Or suddenly a USB HUB would not be recognized or a thumb drive would not show up. I plugged and unplugged different combinations of devices in different orders and ports and nothing really made any sense. I would get to a certain point and then all of a sudden some devices would not get recognized and come as unknown. It seems to me that this has to be a power supply issue, because last night I removed all devices and plugged in just 2 powered hubs. I plugged all the devices into the hubs only and none into the computer directly and everything was recognized properly and is booting and running fine. Does this make any sense? I have had USB problems in the past and resolved them by removing USB hubs not adding them. Here is the list of the USB devices: Canon Printer, Maxtor External Drive, Acom External Drive, Epson Scanner, Logitech Web Cam, Sailtek Joystick, Foot Peddles, Huey monitor color correction tool, and 2 1gig PNY thumb drives.
I would have thought that the power output available at each USB port would be isolated and not a cumulative effect. Does anyone have any ideas here? The main power supply is 460 watts.