Re: How to change BIOS Boot Sequence programmatically.


Sjouke Burry wrote:
san wrote:
William J. Leary Jr. wrote:

"san" <nowsanb4u@xxxxxxxxxxxxxx> wrote in message
news:1154027516.224971.275670@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Can anybody suggest me how to programmatically change BIOS boot
sequence using Assembly language or C programming language. I got some
information like we can access CMOS data by send address to port 70h
and receiving data through port 71h. But i dont boot sequence address
in CMOS memory map.

Here's a couple of examples of CMOS memory maps:

http://www.bioscentral.com/misc/cmosmap.htm
http://ivs.cs.uni-magdeburg.de/~zbrog/asm/cmos.html

Note, for example. in the second reference that location 1DH shows six
different definitions, depending on what machine it resides. Only one of those
six influence which disk boots first.

However, having the map is probably not going to help you much. Both for the
above reason and because on most machines which can have the boot order set,
the information is stored along with the ESCD in the BIOS Flash part. It not
clear to me if it's part of the ESCD, or it's just stored in the same block of
Flash. You'd need flash read/write code and, again, to know the map used for
setting boot order in that block.

I see from your later message that you want to force a network boot. You may
find these interesting:

http://www.pcguide.com/ref/mbsys/bios/boot.htm
http://www.pcguide.com/ref/mbsys/bios/set/adv_Boot.htm

In most of the system I've seen which did network boot, the network card had a
BIOS ROM of it's own which was attached to the boot sequence during BIOS
initialization. It would become the first bootable device, but with boot
turned off by default. If you wanted to perform a network boot, you had to
enter the network cards BIOS setup and to turn on, and often configure, it's
boot features. On systems with integrated network controllers, this setup is
sometimes integrated directly into the standard BIOS setup screens.

- Bill

Thank you for the response. but I have checked last week the address
1DH taking Phoenix CMOS memory in www.bioscentral.com. But it is
showing '00' in my system. I had dumped CMOS data to a file and
observed. But some commercial software are doing this.Actually there is
one more memory address 2DH and its Data 5th bit used for boot order. I
checked that one also but is of no use.

Try and find a cmos saver program.
then save each bios configuration you want to
a file.
Restoring the appropriate file to bios, will
boot to the correct device.
Google for cmos14.zip,it will lead you to simtel

I tried this but not working. My Machine is Acer Aspire 1640 model
laptop with Phoenix BIOS.

.

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