>>337
ttp://www.jp.freebsd.org/www.FreeBSD.org/releases/5.3R/errata.html
より引用。

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(31 Oct 2004, updated on 5 Nov 2004) For FreeBSD/i386 and FreeBSD/amd64, when
installing FreeBSD 5.3 using an USB keyboard the keyboard will stop working
once the kernel boots, because a PS/2 keyboard is always considered to be
attached. As a workaround, select ``Escape to loader prompt'' in the boot
loader menu and enter the following lines at the prompt:

set hint.atkbd.0.flags="0x1"
boot

Note that if you use the boot floppies, this is set by default.

After the installation, add the following line to /boot/loader.conf:

hint.atkbd.0.flags="0x1"
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……つーか、全く同じ書き込みをどっかのスレでした記憶があるぞ。