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Using USB Hubs with Legacy (Serial, Parallel, and
PS/2) Ports
A number of products on the market enable you to connect various
legacy products to USB ports. The most economical way to connect
serial, parallel, or PS/2-port products is through the use of a multipurpose
hub that also features multiple USB ports.
You can also purchase serial-to-USB or parallel-to-USB converter
cables, but these are less flexible and more expensive if you need to
connect multiple legacy devices to a system.
Check the list of supported legacy devices before you buy a converter
cable or multi-purpose port. USB hubs with PS/2 and serial
ports normally support legacy devices such as modems, keyboards,
and mice; USB hubs with parallel ports normally support printers.
If you use other types of parallel devices, such as drives or scanners,
you will need an actual parallel port to connect them. However,
because daisy-chaining multiple parallel devices can be difficult,
moving the printer to a multi-purpose USB hub can free up the LPT
port for use by these other devices.
Online Sources for Additional USB Support
• Linux USB Device Support and Status
http://www.qbik.ch/usb/devices/
• USB News and Troubleshooting Sites
http://www.usbman.com/
http://www.usbworkshop.com/
http://www.usb.org
Universal Serial Bus 209
USB 2.0
USB 2.0 is a backward-compatible extension of the USB 1.1 specification
that uses the same cables, connectors, and software interfaces,
but which runs 40 times faster than the original 1.0 and 1.1 versions.
All existing USB 1.1 devices will work in a USB 2.0 bus because USB
2.0 supports all the slower-speed connections. USB data rates are
shown in Table 8.3.
Table 8.3 USB Data Rates
Interface Megabits per Second Megabytes per Second
USB 1.1 low-speed 1.5Mbit/sec 0.1875MByte/sec
USB 1.1 high-speed 12Mbit/sec 1.5MByte/sec
USB 2.0 480Mbit/sec 60MByte/sec