How does the computer know which one?

Suppose I have two hard drives mounted internally.

And further suppose that each is bootable. (New SSD and original
magnetic HD.)

How does the computer know which one to boot from?

In the old days, there used to be jumpers on the drives and you would
set one to be primary, but I haven't seen that for decades!!

Thanks.

Stormin' Norman wrote on 4/17/2015 11:23 AM:
On Fri, 17 Apr 2015 11:17:53 -0400, Alek wrote:

Suppose I have two hard drives mounted internally.

And further suppose that each is bootable. (New SSD and original
magnetic HD.)

How does the computer know which one to boot from?

In the old days, there used to be jumpers on the drives and you would
set one to be primary, but I haven't seen that for decades!!

Thanks.


The answer to your question:

http://www.howtogeek.com/129815/begi...omputers-bios/


I don't have a BIOS; I have a UEFI. And it doesn't list every drive AFAIK.

On 17/04/2015 16:45, Alek wrote:
Stormin' Norman wrote on 4/17/2015 11:23 AM:
On Fri, 17 Apr 2015 11:17:53 -0400, Alek wrote:

Suppose I have two hard drives mounted internally.

And further suppose that each is bootable. (New SSD and original
magnetic HD.)

How does the computer know which one to boot from?

In the old days, there used to be jumpers on the drives and you would
set one to be primary, but I haven't seen that for decades!!

Thanks.


The answer to your question:

http://www.howtogeek.com/129815/begi...omputers-bios/


I don't have a BIOS; I have a UEFI. And it doesn't list every drive AFAIK.

You do have a BIOS, and its the UEFI BIOS.
You will have to do some searching to find a list of drives to boot
from. If you can't see it , you will have to do some enabling of the
different options etc until it does show.

If you don't know what you are doing, make a backup first.

BobH wrote on 4/17/2015 11:53 AM:
On 17/04/2015 16:45, Alek wrote:
Stormin' Norman wrote on 4/17/2015 11:23 AM:
On Fri, 17 Apr 2015 11:17:53 -0400, Alek wrote:

Suppose I have two hard drives mounted internally.

And further suppose that each is bootable. (New SSD and original
magnetic HD.)

How does the computer know which one to boot from?

In the old days, there used to be jumpers on the drives and you would
set one to be primary, but I haven't seen that for decades!!

Thanks.


The answer to your question:

http://www.howtogeek.com/129815/begi...omputers-bios/


I don't have a BIOS; I have a UEFI. And it doesn't list every drive AFAIK.

You do have a BIOS, and its the UEFI BIOS.

Not according to MS:

"UEFI (Unified Extensible Firmware Interface) is a standard firmware
interface for PCs, designed to replace BIOS (basic input/output system). "

On Fri, 17 Apr 2015 12:00:35 -0400, Alek
wrote:

BobH wrote on 4/17/2015 11:53 AM:
On 17/04/2015 16:45, Alek wrote:
Stormin' Norman wrote on 4/17/2015 11:23 AM:
On Fri, 17 Apr 2015 11:17:53 -0400, Alek wrote:

[snip]

I don't have a BIOS; I have a UEFI. And it doesn't list every drive AFAIK.

You do have a BIOS, and its the UEFI BIOS.

Not according to MS:

"UEFI (Unified Extensible Firmware Interface) is a standard firmware
interface for PCs, designed to replace BIOS (basic input/output system). "

It is an enhanced BIOS.

Sincerely,

Gene Wirchenko

On 4/17/2015 8:45, Alek wrote:
Stormin' Norman wrote on 4/17/2015 11:23 AM:
On Fri, 17 Apr 2015 11:17:53 -0400, Alek wrote:

Suppose I have two hard drives mounted internally.

And further suppose that each is bootable. (New SSD and original
magnetic HD.)

How does the computer know which one to boot from?

In the old days, there used to be jumpers on the drives and you would
set one to be primary, but I haven't seen that for decades!!

Thanks.


The answer to your question:

http://www.howtogeek.com/129815/begi...omputers-bios/


I don't have a BIOS; I have a UEFI. And it doesn't list every drive AFAIK.

"BIOS", like "Kleenex"(TM), has taken on a generic meaning.

It is often used to mean the motherboard firmware that provides the
interface between the OS and the hardware (and some other services),
regardless of whether it is an old-fashioned BIOS or a new UEFI BIOS.

It can be convenient, so get used to it, you'll feel better :-)

--
Gene E. Bloch (Stumbling Bloch)

Alek wrote:
BobH wrote on 4/17/2015 11:53 AM:
On 17/04/2015 16:45, Alek wrote:
Stormin' Norman wrote on 4/17/2015 11:23 AM:
On Fri, 17 Apr 2015 11:17:53 -0400, Alek wrote:

Suppose I have two hard drives mounted internally.

And further suppose that each is bootable. (New SSD and original
magnetic HD.)

How does the computer know which one to boot from?

In the old days, there used to be jumpers on the drives and you would
set one to be primary, but I haven't seen that for decades!!

Thanks.

The answer to your question:

http://www.howtogeek.com/129815/begi...omputers-bios/

I don't have a BIOS; I have a UEFI. And it doesn't list every drive AFAIK.

You do have a BIOS, and its the UEFI BIOS.

Not according to MS:

"UEFI (Unified Extensible Firmware Interface) is a standard firmware
interface for PCs, designed to replace BIOS (basic input/output system). "


Look for the popup boot key.

On my Asus motherboard with UEFI underpinnings, that is the F8 key.

You must press F8, when the first POST text appears. The page
of text that tells you the amount of memory. If your timing isn't
just right, the computer can use the actual boot settings
you defined in the UEFI setup screen.

Popup boot is for defining "transient" boot activities. Say I
have a dual boot computer, I boot Windows in the morning and
Linux in the afternoon. In the morning, near lunch hour, I
do a restart in Windows, the screen goes dark, the first
POST text starts to appear, I hit F8, the little rectangular
boot menu eventually appears (after the disk detection
phase and printout on the screen). I can then select
my Linux disk and boot from that.

When you dual boot via two OSes stored on the same hard
drive, then you are using the same boot definition every
time in the BIOS level, and a "boot manager" installed
by one of the two OS installations, it "owns" the hard drive,
and provides a sub-menu for selection of the OS. So in that
situation (person who puts many OSes on a single drive),
popup boot is worthless. But if you manage the OSes
as "one OS per hard drive", F8 popup boot is your friend.

Defining the default (or semi-permanent) choice in the
BIOS setup screens, is for people who uni-boot and always
want the same OS each time. They don't need F8. They may
use F8, if they need to boot from a CD, or perhaps the
CD is first in the boot order, and boots anyway as
part of the boot priority defined in the BIOS.

Traditionally (mostly modern computers, not 15 year old stuff),
you have one list which is your list of disk drives, as
well as classes of devices. You can put "any optical"
in front of "any hard drive". And the optical and
hard drives can have their own lists. If I display all
that information in one drawing, it looks like this.

Any optical (CR52-M, GH22LP20)
Any hard drive (WD2002FAEX, ST3500418AS)
Floppy
USB mumble...

I can move the hard drive group, in front of the
optical ones if I want.

And within each major category, I can define a priority.
My CR52-M tray is checked for a boot CD, before
my other optical drive.

For example, with the above definition, say I have
no media in either optical drive tray. Priority
skips optical completely and moves to hard drive next.

Say that WD2002 doesn't have any MBR boot code. Maybe
the BIOS then skips that (data-only) drive and it
looks at the ST3500418 drive instead. And if none of
those drives are bootable (as determined by some means),
the BIOS might eventually look at my USB section.

The advantage of popup boot, is if you connect your USB
Linux key, you can press F8, cursor down to the USB
key in the menu, and boot from it. No need to enter the
BIOS setup screens at all. Note that my permanent boot
settings as shown above, a USB key would not naturally
get a chance to boot at all. Using F8 popup, is how I give it
enough (instant) priority, so it wins.

Different brands, use different popup keys. On computers
here, this includes F2, F8, F12, as a function of brand.
Maybe with Asus, it is always F8.

Paul

Paul wrote:
Alek wrote:
BobH wrote on 4/17/2015 11:53 AM:
On 17/04/2015 16:45, Alek wrote:
Stormin' Norman wrote on 4/17/2015 11:23 AM:
On Fri, 17 Apr 2015 11:17:53 -0400, Alek
wrote:

Suppose I have two hard drives mounted internally.

And further suppose that each is bootable. (New SSD and original
magnetic HD.)

How does the computer know which one to boot from?

In the old days, there used to be jumpers on the drives and you would
set one to be primary, but I haven't seen that for decades!!

Thanks.

The answer to your question:

http://www.howtogeek.com/129815/begi...omputers-bios/


I don't have a BIOS; I have a UEFI. And it doesn't list every drive
AFAIK.

You do have a BIOS, and its the UEFI BIOS.

Not according to MS:

"UEFI (Unified Extensible Firmware Interface) is a standard firmware
interface for PCs, designed to replace BIOS (basic input/output
system). "


Look for the popup boot key.

On my Asus motherboard with UEFI underpinnings, that is the F8 key.

You must press F8, when the first POST text appears. The page
of text that tells you the amount of memory. If your timing isn't
just right, the computer can use the actual boot settings
you defined in the UEFI setup screen.

Popup boot is for defining "transient" boot activities. Say I
have a dual boot computer, I boot Windows in the morning and
Linux in the afternoon. In the morning, near lunch hour, I
do a restart in Windows, the screen goes dark, the first
POST text starts to appear, I hit F8, the little rectangular
boot menu eventually appears (after the disk detection
phase and printout on the screen). I can then select
my Linux disk and boot from that.

When you dual boot via two OSes stored on the same hard
drive, then you are using the same boot definition every
time in the BIOS level, and a "boot manager" installed
by one of the two OS installations, it "owns" the hard drive,
and provides a sub-menu for selection of the OS. So in that
situation (person who puts many OSes on a single drive),
popup boot is worthless. But if you manage the OSes
as "one OS per hard drive", F8 popup boot is your friend.

Defining the default (or semi-permanent) choice in the
BIOS setup screens, is for people who uni-boot and always
want the same OS each time. They don't need F8. They may
use F8, if they need to boot from a CD, or perhaps the
CD is first in the boot order, and boots anyway as
part of the boot priority defined in the BIOS.

Traditionally (mostly modern computers, not 15 year old stuff),
you have one list which is your list of disk drives, as
well as classes of devices. You can put "any optical"
in front of "any hard drive". And the optical and
hard drives can have their own lists. If I display all
that information in one drawing, it looks like this.

Any optical (CR52-M, GH22LP20)
Any hard drive (WD2002FAEX, ST3500418AS)
Floppy
USB mumble...

I can move the hard drive group, in front of the
optical ones if I want.

And within each major category, I can define a priority.
My CR52-M tray is checked for a boot CD, before
my other optical drive.

For example, with the above definition, say I have
no media in either optical drive tray. Priority
skips optical completely and moves to hard drive next.

Say that WD2002 doesn't have any MBR boot code. Maybe
the BIOS then skips that (data-only) drive and it
looks at the ST3500418 drive instead. And if none of
those drives are bootable (as determined by some means),
the BIOS might eventually look at my USB section.

The advantage of popup boot, is if you connect your USB
Linux key, you can press F8, cursor down to the USB
key in the menu, and boot from it. No need to enter the
BIOS setup screens at all. Note that my permanent boot
settings as shown above, a USB key would not naturally
get a chance to boot at all. Using F8 popup, is how I give it
enough (instant) priority, so it wins.

Different brands, use different popup keys. On computers
here, this includes F2, F8, F12, as a function of brand.
Maybe with Asus, it is always F8.

Paul


It takes some time to adjust to the UEFI F8 Boot-Device mode on my Asus
board (Boot devices during startup by pressing F8 when the Asus Logo
appears).
- Disabling the logo with Fast Boot and Hardware Fast Boot options
enabled necessitates almost exact timing to access the Boot-device menu.
Even without FB/HFB when being marginally late pressing F8 (after
POST) and the Windows pre-o/s load F8 Safe Mode options are present.

Safe Mode is also available by F5 during startup when the Asus Logo appears.



--
...winston
msft mvp consumer apps

On Fri, 17 Apr 2015 11:50:08 -0700, Gene Bloch wrote:

On 4/17/2015 8:45, Alek wrote:
Stormin' Norman wrote on 4/17/2015 11:23 AM:
On Fri, 17 Apr 2015 11:17:53 -0400, Alek wrote:

Suppose I have two hard drives mounted internally.

And further suppose that each is bootable. (New SSD and original
magnetic HD.)

How does the computer know which one to boot from?

In the old days, there used to be jumpers on the drives and you would
set one to be primary, but I haven't seen that for decades!!

Thanks.


The answer to your question:

http://www.howtogeek.com/129815/begi...omputers-bios/


I don't have a BIOS; I have a UEFI. And it doesn't list every drive AFAIK.

"BIOS", like "Kleenex"(TM), has taken on a generic meaning.

It is often used to mean the motherboard firmware that provides the
interface between the OS and the hardware (and some other services),
regardless of whether it is an old-fashioned BIOS or a new UEFI BIOS.

It can be convenient, so get used to it, you'll feel better :-)

BTW, the next time I booted my computer I pressed Delete in the UEFI
screen to see what Asus thinks...

The UEFI configuration screens identifies itself as "UEFI BIOS".

The original BIOS wasn't UEFI - that came after an update.

The MB is an Asus P8 H67-M EVO.

--
Gene E. Bloch (Stumbling Bloch)

.. . .winston wrote on 4/18/2015 3:27 AM:

major snip

It takes some time to adjust to the UEFI F8 Boot-Device mode on my Asus
board (Boot devices during startup by pressing F8 when the Asus Logo
appears).
- Disabling the logo with Fast Boot and Hardware Fast Boot options
enabled necessitates almost exact timing to access the Boot-device menu.
Even without FB/HFB when being marginally late pressing F8 (after
POST) and the Windows pre-o/s load F8 Safe Mode options are present.

Safe Mode is also available by F5 during startup when the Asus Logo appears.

I have a Dell desktop. F12 is for the so-called boot menu and F2 brings
up the firmware setup (nee BIOS).

I have to start tapping one of them as soon as the Dell logo appears and
not stop until it disappears.

The boot menu screen says...

Boot mode is set to UEFI with Legacy OPROM; Secure boot: OFF

UFI BOOT:
Windows Boot Manager
UEFI: Toshiba
UEFI: Generic External 1.03 The SSD
LEGACY BOOT:
P01: WDC WD6400AAKS-00A780
TOSHIBA
Generic External 1.03
FANTOM HDS....
P1: PLDS DVD+/-RW ...
OTHER OPTIONS
BIOS Setup
Diagnostics
Peripheral Device Setting (OPROM Setting)
Change Boot Mode Setting