install FreeBSD, Linux, and Windows 95 on them.</para>

install FreeBSD, Linux, and Windows 95 on them.</para>

<para>Here's how I might do it using these hard disks:

<para>Here's how I might do it using these hard disks:

<itemizedlist>

<itemizedlist>

<listitem>

<listitem>

</listitem>

</listitem>

</itemizedlist>

</itemizedlist>

<para>Both disks have 1416 cylinders.</para>

<para>Both disks have 1416 cylinders.</para>

restricts users of this interface (i.e. boot managers hooked into

restricts users of this interface (i.e. boot managers hooked into

your disk's MBR as well as OS loaders hooked into the Boot Sectors)

your disk's MBR as well as OS loaders hooked into the Boot Sectors)

to the following limits:

to the following limits:

<itemizedlist>

<itemizedlist>

<listitem><para>1024 cylinders, max</para></listitem>

<listitem><para>1024 cylinders, max</para></listitem>

<listitem><para>256 heads    , max</para></listitem>

<listitem><para>256 heads    , max</para></listitem>

<listitem><para>64 sectors/track, max (actually 63, <literal>0</> isn't

<listitem><para>64 sectors/track, max (actually 63, <literal>0</> isn't

available)</para></listitem>

available)</para></listitem>

</itemizedlist>

</itemizedlist>

<para>Now big hard disks have lots of cylinders but not a lot of

<para>Now big hard disks have lots of cylinders but not a lot of

heads, so invariably with big hard disks the number of cylinders is

heads, so invariably with big hard disks the number of cylinders is

boot manager and the OS loader hooked into all bootable partitions'

boot manager and the OS loader hooked into all bootable partitions'

Boot Sectors) has to reside below cylinder 1024.  In fact, if your

Boot Sectors) has to reside below cylinder 1024.  In fact, if your

hard disk is typical and has 16 heads, this equates to:

hard disk is typical and has 16 heads, this equates to:

<informalexample>

<informalexample>

<para>1024 cyl/disk &times; 16 heads/disk &times; 63 sect/(cyl-head)

<para>1024 cyl/disk &times; 16 heads/disk &times; 63 sect/(cyl-head)

&times; 512 bytes/sector</para>

&times; 512 bytes/sector</para>

</informalexample>

</informalexample>

<para>which is around the often-mentioned 528MB limit.</para>

<para>which is around the often-mentioned 528MB limit.</para>

<para>To use my 1.6 Gig Western Digital as an example again, it's

<para>To use my 1.6 Gig Western Digital as an example again, it's

physical geometry is:

physical geometry is:

<informalexample>

<informalexample>

<para>(3148 cyl, 16 heads, 63 sectors/track, 512 bytes/sector)</para>

<para>(3148 cyl, 16 heads, 63 sectors/track, 512 bytes/sector)</para>

</informalexample>

</informalexample>

<para>However, my BIOS LBA remaps this to:

<para>However, my BIOS LBA remaps this to:

<informalexample>

<informalexample>

<para>( 787 cyl, 64 heads, 63 sectors/track, 512 bytes/sector)</para>

<para>( 787 cyl, 64 heads, 63 sectors/track, 512 bytes/sector)</para>

</informalexample>

</informalexample>

<para>giving the same effective size disk, but with cylinder and head

<para>giving the same effective size disk, but with cylinder and head

counts within the BIOS API's range (Incidentally, I have both Linux and

counts within the BIOS API's range (Incidentally, I have both Linux and

<para>For reference, the following boot managers use the

<para>For reference, the following boot managers use the

Master Boot Sector to store their code and data:

Master Boot Sector to store their code and data:

<itemizedlist>

<itemizedlist>

<listitem>

<listitem>

</listitem>

</listitem>

</itemizedlist>

</itemizedlist>

<para>These boot managers use a few additional sectors after the

<para>These boot managers use a few additional sectors after the

Master Boot Sector:

Master Boot Sector:

<itemizedlist>

<itemizedlist>

<listitem>

<listitem>

</listitem>

</listitem>

</itemizedlist>

</itemizedlist>

</sect3>

</sect3>

<para>If you have a bootable DOS partition on your disk, you can boot

<para>If you have a bootable DOS partition on your disk, you can boot

off a DOS floppy, and run:

off a DOS floppy, and run:

<informalexample>

<informalexample>

<screen>A:\> <userinput>FDISK /MBR</></screen>

<screen>A:\> <userinput>FDISK /MBR</></screen>

</informalexample>

</informalexample>

<para>to put the original, simple DOS boot code back into the system.  You can

<para>to put the original, simple DOS boot code back into the system.  You can

then boot DOS (and DOS only) off the hard drive.  Alternatively, just

then boot DOS (and DOS only) off the hard drive.  Alternatively, just