[ILUG] Grub (was: 4 Operating systems)

[Brian Foster]

  > From: "Matthew French" <mfrench42 at yahoo.co.uk>
  > Date: Tue, 19 Feb 2002 17:31:00 -0000
  > 
  >[ ... ]  Grub screws up the power management on my Compaq laptop. While it
  > might be nice in theory, I cannot see why a boot loader has to interfere
  > with power management? Surely that is the OS's responsibility.

 I do not know, but I can guess --- my guess is based on the Power Management
 I implemented for a commercial x86 Unix some years ago ....

  CAVEAT: that was a _long_ time ago, and my memory is probably more confused
          than usual ....   ;-\ 

 as I recall, the only(?) reason the boot-loader is (must be) involved is
 because the default Power Management API is 16-bit Real Mode.  but any
 sensible O/S is booted in, and runs in, 32-bit Virtual.  hence, the boot
 loader --- which starts in 16-bit Real --- has to, as one of its tasks
 before changing to 32-bit Virtual, call the APM BIOS and toggle(?) it
 into 32-bit Virtual.

 the boot loader can, and arguably should, do other things.  e.g., if this
 is a laptop using battery power, and the batteries are (almost) exhausted,
 it may be unwise to continue the boot --- the system will go down very
 quickly, needlessly risking file-system corruption et.al.  so, e.g., in
 the system I implemented, it was possible to configure the boot-loader
 with a rule describing when the system should/shouldn't be booted (this
 example is not quite the exact syntax, but close):

   apm.enabled & ! ac.power & (battery.status = critical | battery < 5%) => ! boot

 meant that if APM is in use, you're not using the A/C mains (and hence are
 using the battery), and either of the two methods of estimating the battery's
 power reserves suggests the battery is (just about) dead, then don't boot.
 of course, this rule could be overridden.

 whilst APM has changed quite a bit since those days, I suspect these points
 still apply.  what I don't know is why `grub' f***s up on your system; or,
 why, on my system, if APM is enabled, starting X11 hangs the system hard.  ;-(

cheers!
	-blf-
--
 Innovative, very experienced, Unix and      | Brian Foster    Dublin, Ireland
 Chorus (embedded RTOS) kernel internals     | e-mail: blf at utvinternet.ie
 expert looking for a new position ...       | mobile: (+353 or 0)86 854 9268
  For a resume, contact me, or see my website  http://www.blf.utvinternet.ie