On Mon, 29 Jun 2015 16:57:18 -0400, rickman Gave us:
It boils down to the fact that the "boot sector" location is standardized.
So the "system" "looks" for any mass storage device with boot info, and provides a list of availability and also chooses a default if no menu for selection is presented.
rPi model A will boot from directly connected USB storage (ie. no USB hub) model B has same BIOS, but has a hub on-board, so won't boot from USB.
but RPI doesn't really have a BIOS, it has a boot-loader which runs on the GPU, the rest is all OS
-- umop apisdn
Debug.exe on DOS talks to the PC BIOS the XP vesion talks to the NT kernel, hence the altered drive numbering for hard disks.
No.
-- umop apisdn
You're thinking at too high a level; talk to the *controller* (i.e., use "I " and "O " not "W ", etc.) Query and direct the *controller* to see what *it* thinks is attached.
Then how is it possible to boot ffrom USB ?
Den tirsdag den 30. juni 2015 kl. 20.41.26 UTC+2 skrev snipped-for-privacy@gmail.com:
the bios see a usbdrive, the usbdrive see a harddisk
-Lasse
Some newer motherboards (many, I think) do have the ability to enumerate the USB from within the BIOS, and map USB-attached mass storage devices into the BIOS hard-drive system. On these systems it's usually possible to boot from USB devices.
On older motherboards, this doesn't happen - USB mass storage devices aren't seen as "disks" by the BIOS. On these motherboards you can't boot from USB.
In both cases, once Linux boots, the BIOS support for USB disks (present or absent) is no longer relevant. Linux enumerates the USB itself, and accesses USB mass-storage devices directly via the bus. The only further use of the BIOS-level USB support (as far as I know) is when you install a bootloader such as GRUB... Linux will try to figure out what BIOS drive identifier is used for each device so that it can set up the boot configuration properly.
On Tue, 30 Jun 2015 11:41:22 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:
IF there is a bootable sector on the device, the BIOS OF THAT DEVICE reports it as bootable to the polling device (the motherboard), and modern Motherboards add it to their list of devices capable of starting an operating system... It then boots whichever is first in their set-up list, OR provides a selection menu for the operator to choose from.
IF I place a USB device ahead of my CD/DVD ROM device and HD device (in the motherboard's BIOS setup) That is the order devices get booted from, IF such a device is in place at boot time. The BIOS looks no further than a volume's boot sector, or in the case of USB, it gets that answer from the USB device itself, as they their own little mini-BIOS.
My stuff is all like five years or older and it can do it. I have a neato little 8 gigger with live Ubuntu on it.
And I would venture to sat that thius differs from BIOS only in terminology.
So it has MORE BIOS than an old 386, it is still an input output system. Does the fact that it runs in more than 64K of RAM make it otherwise ? Maybe :
N.Q.A.B.I.O.S.
Not Quite As Basic Input Output System.
On Tue, 30 Jun 2015 16:29:46 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:
It doesn't perform any mapping. It looks for a bootable device. IF your mobo can do it, it does, but it maps nothing. The USB device itself has its own handler for that. And then Linux takes over.
MOBOs that are able to present a menu at boot time for selection of a boot device are those which can do it. Older MOBOs cannot.. There were some transition MOBOs which "saw" some USB devices as "floppy drives".
On Tue, 30 Jun 2015 16:32:21 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:
I have always hated how motherboards were not "fully explained" in their included manuals.
The RAM settings, PCI bus, etc. Using their integrated "help" text was and still is typically horrendous, and generally just a very cursory description, like a mere listing of your "available" choices "on or off". Never a full description of what is taking place.
They have not been quite basic for quite a long time.
With the new UEFI stuff, it is even more complicated with (some of) them trying to offer mixed use choices.
My MOBO has a hard switch with three positions where I can store three entirely different set-ups and change with the flick of a switch (while off of course).
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