🚀 go-pugleaf

In article <1990Mar10.214534.7611@eagle.lerc.nasa.gov> tpf4434@DOMAIN_2.lerc.nasa.gov () writes:
>In article <2963.25f214c2@crcc.uh.edu> rui@athena.mit.edu (Christopher Tung) writes:
>>Subject:Booting Problem 
>>This may seem like a dumb question, but how do I get my PC Clone to boot
>>from drive b:?  It boots from drive a: , a 5 1/2 HD drive, but it won't
>>boot from drive b: a 
>it's not possible to boot from drive B unless you physically open
>the system unit, and swap the connectors on drive A and B..
>part of IBM's original design of the PC was to disable booting from
>drive B.. you'll never be able to accomplish it..

Interesting, since I've seen ads for programs which claim to let you do this,
and the only way anything that aproaches well behaved knows about the disk
drives is through the bios, It should be possible.

In fact on a 386 it IS possible just by entering proctected mode, and trapping
all i/o commands to the disk drive and rerouting them.  But I think that
this is an extreme case.  For most programs, it is probably sufficient to
install a small tsr in high memory, preferably in some place that won't
get clobbered, and have it intercept all bios disk commands and switch
those destined for drive A to B and vice versa.  After booting off of B,
you may want to have it deactivate itself.  When you do this it may be
necessary to make sure that all other interupts are pointed to the right
locations for a boot, otherwise you may have problems with important
code being overwritten by whatever is loaded from the disk.  It may be
a good idea to put such a program on a boot sector of a disk that
fits in drive A, and reboot off of A which would then automatically
boot off of B.

		Ross Biro bir7@portia.stanford.edu