Best Practices for USB Device Users

Best Practices For USB Device Users




The following document explains several best practices to ensure USB (Universal Serial Bus) devices work optimally:
If a system is booted from a USB device (such as a memory key, USB floppy drive, USB HDD, optical USB drive, etc), the device should be connected to a root port in the system back panel of the system (instead of a USB hub). Connecting a USB bootable device in a USB hub will increase the detection time and power on time of the device and may cause the boot process to timeout.


The USB root port detection order in desktop systems during the boot process is as follows:



Back panel 4-stack USB ports (bottom to top).
System front panel two ports.
Back 2-stack USB ports.


When connecting a USB device to the system that has a legacy ATAPI/EIDE device that serves the same function as another device in the system (such as a USB optical drive and ATAPI/EIDE optical drive), the system BIOS will treat the legacy ATAPI/EIDE device as the higher priority device and detect/enumerate it first. If such a situation arises, the legacy device should be disabled first in the system BIOS.


When booting to a DOS environment, it is recommended to have only the USB boot device, keyboard and mouse connected to the system root ports. Do not connect the keyboard or mouse to separate USB hubs, especially to separate USB 2.0 specification hubs or the front USB connectors in the system. Keyboards and mice are typically USB 1.0/1.1 devices and work on slower speeds. Detecting keyboards and mice in these hubs will take longer and might lead to systems locking during the boot process.


Not all USB devices have drivers native for the Microsoft® Windows® XP or Windows 2000 operating systems. Users will need to install vendor-specific drivers for optimal functionality. Always check for driver availability to any other operating system. When installing a USB device that does not have drivers native to Windows, carefully follow the device manufacturer's instructions. In particular, pay special attention if the drivers must be installed before plugging the device into the USB port for the first time.


Some USB devices and protocols have not been validated by Dell. The most common protocols validated for use on Dell systems are SCSI and ATAPI in USB.


When a USB memory key is attached to a system without a floppy drive, Norton Antivirus (or any other antivirus program) may confuse the memory key as a floppy drive and not allow the system to shutdown properly. Remove the USB key before shutting down the system.


USB hubs in all Dell flat panel monitors follow the USB 2.0 specification.

When a non-bootable USB 2.0 device is attached to the system at same time as a bootable USB 1.1 device, the system will find the USB 2.0 device faster and will fail to boot. Either make to USB 2.0 bootable or remove all the non-bootable USB 2.0 devices before booting to USB 1.1 device.


USB Versions

USB 1.0 - The original release of USB, transferring 12 Mbps.

USB 1.1 - Also known as “full-speed USB”, USB 1.1 is similar to the original release of USB however minor modifications for the hardware and the specifications. This version of USB still only supports a rate of 12 Mbps.

USB 2.0 - USB 2.0 also known as “hi-speed USB”. Hi-speed USB is capable of supporting a transfer rate of up to 480 Mbps. It is backwards compatible meaning it is capable of supporting USB 1.0 and 1.1 devices and cables.