scorpius.txt

The Scorpius loader in extipl 5 is identical to the Extended-IPL
version 4. Since large hard disks became inexpensive and Scorpius
cannot load an OS at the end of a large disk, Scorpius may not be used 
much. We included this document because the default loader Gemini
evolved from Scrorpius.

1. Using Scorpius on a Floppy Disk
To install Scorpius on a floppy, insert formatted disk to A: and type
	extipl fdtest filename-of-floppy-drive @scorpius.
Then Scorpius will be installed to floppy.

Let's use Scorpius on floppy. Make sure that floppy drive is tried
for booting before hard disk. Otherwise you cannot boot from floppy
disk.

Insert the floppy disk and reboot your computer. You should see your computer
boot as usual. Scorpius boot OS as original MBR does unless shift key is
pressed down.

Reboot your computer and see when floppy disk is accessed for booting.
Push down shift key when floppy drive starts reading.  Then partition
information and prompt "Boot#0:0.?" is displayed. In this prompt, the
first 0 stands for hard disk unit 0 (first HD), the second 0 does the
depth of the selected partition table, and ? stands for the partition
selected for booting.  You can select booting partition by typing
1--4. Hitting enter key boots OS in selected partition. A more detailed
usage is given below.

2. Installing Scorpius onto a Hard Disk
Booting from floppy is inconvenient. You may want to install Scorpius
to HD once you convince that it is safe.

To install it to HD, type
	extipl install filename-of-hard-disk @scorpius
Then you are asked to what file MBR is backed up. After backing up,
you are asked for final confirmation. Hitting `y' key allows
Scorpius replace MBR with its own. If you want to stop
installation, type Control-C.

You must log in as root to do the installation.

3. Booting with Scorpius
Scorpius exactly does same thing as original MBR does unless shift key is
pressed down, i.e. it boots OS in the partition marked bootable. To select
booting OS, press down shift key when booting. Then Scorpius displays
contents of partition table and waits for your instruction. Below is an
example.

	-------------------
	Part  Sys
	 1    s01		;; partition NO. and partition ID (DOS)
	 2    sA5		;; FreeBSD
	 3    s05		;; (MS-DOS) extended partition
	 4			;; empty partition
	Boot #0:0.2		;; prompt
	-------------------
	      | | |
	      | | +---- partition NO.
              | +----- the depth of the partition table
	      +------ HD unit NO.

Partition ID below "System" depends on what OS you install in HD. First
selected partition is the partition marked bootable.

In this step you can select booting partition by number 1--4 and hitting enter
key starts booting. If you try to boot empty partition (4 in this case),
you here beep sound and booting does not start. Booting also does not start
if selected partition does not have 0xaa55 in 511th byte, which indicates
it is a valid partition.

Some OS does not boot if its partition is not marked bootable. Scorpius can
mark selected partition bootable before booting. It can be done hitting
end key instead of enter key. Scorpius has 2 kinds of booting key.
They are

	<Enter>	boot OS in selected partition.
	<End>	mark selected partition bootable and boot OS in it. If you
		do not press shift key in next booting, this partition is
		booted. Scorpius can mark partitions bootable only in
		first HD. You cannot mark partitions in second or later
		HD bootable, or an extended partition.

4. Booting OS in the Second or Later Hard Disk
Booting OS in non-first HD is not an official function of PC/AT compatible
computers. Thus not all OS can boot from second or later HD.

In stage of partition selecting, you can select them by inputting number
1 to 4. You can switch target HD by inputting 0. If you input 0, Scorpius
displays contents of partition table of next HD. You can do the same thing with
currently selected HD as first HD except end key. You cannot mark partitions
in second or later HD bootable by end key. When you see the contents of
partition table of second HD and hit 0, you will see that of third HD if
you have it. Otherwise you will return to first HD.

5. Booting from an Extended Parition

If you choose partition 3 in the example in 3.3, Scorpius shows the
partition table in the extended parition 3. Below is an example

	-------------------
	 Part  Sys
	  1    s83		;; partition no. and system ID
	  2    s05		;;
	  3
	  4
	 Boot #0:1.1		;; prompt
	-------------------

In this example, the first partition in the extended partition is a
Linux partition, and the second is an extended partition in the
extended parition. If you select 1, you boot Linux. If you select 2,
you enter the extended partition. In order to return to the primary
partition, select 0 (switching hard drive) several times.

6. Tricky Use of Scorpius
If there are no partitions marked bootable, Scorpius enters
partition selection even if shift key is not pressed. If you want not
to press shift key, you can exploit this feature. You can mark all
partition not bootable by "extipl clrboot" command. If BIOS loader of
MBR checks the validity of MBR strictly, it consider the MBR invalid
and YOU BECOME UNABLE TO BOOT ANY OS IN YOUR HARDDISK. BE CAREFUL.
