1USB Legacy support 2~~~~~~~~~~~~~~~~~~ 3 4Vojtech Pavlik <vojtech@suse.cz>, January 2004 5 6 7Also known as "USB Keyboard" or "USB Mouse support" in the BIOS Setup is a 8feature that allows one to use the USB mouse and keyboard as if they were 9their classic PS/2 counterparts. This means one can use an USB keyboard to 10type in LILO for example. 11 12It has several drawbacks, though: 13 141) On some machines, the emulated PS/2 mouse takes over even when no USB 15 mouse is present and a real PS/2 mouse is present. In that case the extra 16 features (wheel, extra buttons, touchpad mode) of the real PS/2 mouse may 17 not be available. 18 192) If CONFIG_HIGHMEM64G is enabled, the PS/2 mouse emulation can cause 20 system crashes, because the SMM BIOS is not expecting to be in PAE mode. 21 The Intel E7505 is a typical machine where this happens. 22 233) If AMD64 64-bit mode is enabled, again system crashes often happen, 24 because the SMM BIOS isn't expecting the CPU to be in 64-bit mode. The 25 BIOS manufacturers only test with Windows, and Windows doesn't do 64-bit 26 yet. 27 28Solutions: 29 30Problem 1) can be solved by loading the USB drivers prior to loading the 31PS/2 mouse driver. Since the PS/2 mouse driver is in 2.6 compiled into 32the kernel unconditionally, this means the USB drivers need to be 33compiled-in, too. 34 35Problem 2) can currently only be solved by either disabling HIGHMEM64G 36in the kernel config or USB Legacy support in the BIOS. A BIOS update 37could help, but so far no such update exists. 38 39Problem 3) is usually fixed by a BIOS update. Check the board 40manufacturers web site. If an update is not available, disable USB 41Legacy support in the BIOS. If this alone doesn't help, try also adding 42idle=poll on the kernel command line. The BIOS may be entering the SMM 43on the HLT instruction as well. 44 45