From roger@ans.netMon Oct  2 15:17:58 1995
Date: Tue, 22 Aug 1995 13:30:30 -0400 (EDT)
From: Roger Florkowski <roger@ans.net>
To: Paul Mora <paul@hal.mkm.aix.can.ibm.com>
Subject: Re: BSD 4.4 for the RT


> Thanks for the information regarding IDE drives and how to get them to 
> work. I've now got 2 IDE drives in the RT, and was successful in 
> installing BSD-4.4. But, I can't get the machine to boot off the IDE drives.
> 
> Is there something special/unique that I have to do to get them to boot? 
> I noticed that in the initial install, the installboot script failed 
> because it could not match the device type. I looked at the script, and 
> saw that it was just a dd command. I tried to interpret and do the dd 
> manually, but it didn't work. The machine doesn't know what to boot from, 
> and just tries the floppy drive over and over.
> 
> Do I have to use the other programs hddump and mkbrec? If so, how?

Ok, this is pretty simple.  Yes, you need to use mkbrec.
I dont recall (off hand) what the arguments to mkbrec are.
Do a "mkbrec -?" to find out.  You'll supply the number
of heads, cylinders, sectors/track, to mkbrec, and redirect
the output to a file.  The file will be 512 bytes in size.
You'll have to dd this to the disk, like installboot did.
(to the first block on the disk).  Then you'll also
need to dd /usr/mdec/boothd) to a "special spot"
on the disk.   You calculate that spot/offset by multiplying
(4 * number-sectors-per-track).  Then you can use the
second dd-line as the "model" for how to dd the boot-program.

Quick summary:
    -) the RT boot-rom looks at the FIRST BLOCK of the device
	for a "boot record".  The boot record contains information
	about the geometry of the drive, and points to where
	the boot-program is located.   (the AOS default for
	a boot-block is to load the boot-program from the
	4th track.  That is why you multiply (4 * secspertrack)
	to find the offset where boothd should be dd'ed to.
	mkbrec was written to conform with AOS specs.)
    -) the RT boot-rom then loads the boot-program from the
	location specified in the boot-block, and runs it.
    -) this is the AOS "first-level-boot" program.  It has
	no console support, and its only purpose in life
	is to find a root filesystem and a program called
	/boot.
    -) the AOS first-level-boot-program then loads /boot
	and executes it.  This is the second-level-boot program.
	It also happens to be the same program that is on
	the SAUTIL diskette.
    -) this program will then load and execute /vmunix.


> Thanks again,

No problem.  Write back if you have any questions, etc.

ROg.

-- 
Roger Florkowski   -   Advanced Network & Services, Inc.   -   roger@ans.net