Sergey Babkin skrev:
From: Peter Jeremy <[EMAIL PROTECTED]>
Some time ago, I was surprised to find that my son's oldish (mid 2003)
system was happy to try and boot off a USB memory stick.
The BIOSes have been able to do this feat for a while now. There are two
caveats though:
1. It's slow, since BIOSes tend to use USB 1.x speeds,
and even that not in a really fast way. So the big
images are best to be avoided. Though probably it's
still faster than floppies.
2. Accessing the root filesystem - the USB drivers
have to be either statically compiled into the
kernel or be loaded by the boot loader through BIOS
(maybe through an analog of initrd ram disk - I'm
not sure what advances have been done to the FreeBSD
boot loader nowadays).
There is another major caveat for some BIOSes:
3. The BTX loader is a 32-bit program that calls the BIOS functions via
v86 calls, these calls fails on some BIOSes when a disk/cd is attached
with USB resulting in the infamous BTX halted error.
I've been told that this is due to the fact that the BIOS tries to enter
32-bit mode again not realizing that the CPU already is in this mode.
I recently found out that there is something called BIOS32, a 32-bit
interface to the BIOS functions. More info here:
http://www.mega-tokyo.com/osfaq2/index.php/I%20heard%20you%20can%20do%20PCI%20calls%20with%20the%20BIOS%20in%20Protected%20Mode%3F
I haven't had time to see if calling the function that blows up when
booting from USB-CD (check which drives are available) thru BIOS32 is
going to work or not.
I have lots of boards that have this problem (Supermicro P8SCi for one),
if someone wants to have any changes tested. I thought using a USB thumb
drive instead of a CD-RW would be easier but I haven't had time to do
anything with yet.
/Martin
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