Input Devices - Upgrading and Repairing PCs - page 757

well as the keyboard and mouse ports. Many systems and motherboards still include one or two PS/2
ports (now called legacy ports) as well as USB, but many modern systems and replacement
motherboards are legacy-free systems that have no PS/2 ports and use only USB ports for interfacing
keyboards and mice.
Virtually all keyboard manufacturers now market USB keyboards, but if you want to use your
keyboard with both legacy (PS/2) and legacy-free (USB) systems, the most economic way to do so is
to specify a keyboard that includes both a USB connector and an adapter to permit the keyboard to
work with PS/2 ports.
Although rare in modern systems, some older systems don't accept USB keyboards, even those with
USB ports, because the original PC BIOS has a keyboard driver that expects a standard keyboard port
interface to be present. When a USB keyboard is installed on a system that lacks USB keyboard
support, the system can't use it because no driver exists in the BIOS to make it work. In fact, some
systems see the lack of a standard keyboard as an error and halt the boot process until one is
installed.
To use a keyboard connected via the USB port, you must meet three requirements:
• Have a USB port in the system.
• Run Microsoft Windows 98 or newer. (Previous versions did not include USB keyboard
drivers.)
• Have a system chipset and BIOS that feature USB Legacy (keyboard and mouse) support.
USB Legacy support means your motherboard has a chipset and ROM BIOS drivers that enable a
USB keyboard to be used outside the Windows graphical user interface (GUI) environment. Almost
all 1998 and newer systems with USB ports include a chipset and BIOS with USB Legacy (meaning
USB Keyboard) support, although it might be disabled in the BIOS Setup.
Even though USB Legacy support enables you to use a USB keyboard in almost all situations, don't
scrap your standard-port keyboards just yet. If the system has PS/2 keyboard and/or mouse ports, they
may need to be used when running hardware diagnostics, flashing the motherboard ROM BIOS, or
troubleshooting USB keyboard and mouse issues. I've also had to use PS/2 keyboards and mice when
installing older Windows versions on newer systems, due to the lack of proper support until the
chipset USB drivers are installed. A good PC tech always has PS/2 keyboards and mice on hand for
testing.
If you have problems with USB keyboards and mice (USB Legacy support), look at these possible
solutions:
• Microsoft's Knowledge Base ( http://support.microsoft.com ) might have an article that
addresses your problem.
• Your keyboard or mouse vendor might offer new drivers.
• Your system or motherboard manufacturer might have a BIOS upgrade you can install.
• Check the BIOS Setup to be sure USB keyboard and mouse support is enabled.
• As a fallback, connect the keyboard to the PS/2 port with an adapter, or use a PS/2 keyboard
and mouse until you resolve the problem.
See the Chapter 14 section, “ Universal Serial Bus (USB) ,” p. 704 .
Keyboards with Special Features