USB booting
From Grub4Dos Wiki
←Older revision | Newer revision→
Contents |
BIOS USB booting "standards"
Booting from CD is standardized, called eltorito. For BIOS and USB there are no standards. This brings a lot of confusion.
There are two different things. USB booting and USB legacy support.
Most BIOS's I've seen have either the one or the other way implemented.
USB booting by BIOS
The defacto standard while USB booting is to assign either (hd0), (fd0) or (cd0) [depending if booting USB-HDD (including flash), USB-FDD or USB-CDROM]. The BIOS will make the device available via the standard BIOS interrupt calls.
That's why legacy operating systems not aware of USB like DOS may boot from this device as it would be a normal internal harddisk. This works very well for booting any operating system.
USB legacy support
This is not so often supported. It's basically a great idea. You can boot like normal form any media such as internal harddisk (hd0) and USB devices will be accessible for legacy operating systems not aware of USB system thought a drive letter (even if you haven't boot them).
When using USB legacy support the USB harddisk can be seen in some BIOS in the boot order. BIOS can boot now the device supported by USB legacy support. But this is quite problematic, things working with normal USB booting by BIOS like XP/USBoot will not work when BIOS is booting a device detected by USB legacy support, in this cases even PLoP works better when USB legacy support is turned off.
USB booting with no BIOS support or with buggy BIOS
See PLoP Bootmanager (BIOS Extender)
Windows XP
XP has also no native support for booting or installing to USB. This is not BIOS or bootmanager's fault. Bootstrapping with BIOS functions is working but the direct harddisk access driver isn't available and this results in a bluescreen.
To overcome this you can either google a lot and do the manual way or use usboot.org 2.x and follow the instructions.
portability
Even if it's booting fine on your machine this doesn't mean it will work well in combination with any foreign machine. XP is not the best operating system for USB, rather try also DOS and Linux at least for reference.
some notices about USB booting
- USB Keyboard and/or USB Mouse must be activated in BIOS
- if booted from USB and Keyboard and Mouse emulation is enabled then SBLive! drivers will not load
- if booted from eSATA and keybord and mosue emulation are enabled then DOS games will stock from time to time
- USBoot 2.08.zip does not alter MBR nor VBR
- USB not booting if USB HUB with it's own power is connected
- Even if computer is powered off and the USB HDD will have power... If USB HUB with it's own power supplement is connected the USB HDD is not bootable.
- internal USB cardreader is only seen in BIOS when USB hub is NOT connected
- my internal USB multicardreader is NOT bootable even if USB-HDD's are bootable
- try to remove ANY other USB device while trying to boot USB (yes, confirmed)
Links
- http://home.graffiti.net/jaclaz:graffiti.net/Projects/USB/USBstick.html (read at minimum from "Even if the motherboard supports USB booting, its implementation may be defective, results and direct observation lead to find that there are motherboards with one or more of the following “defects”:" the following 1 - 8)
- http://home.graffiti.net/jaclaz:graffiti.net/Projects/USB/USBfaqs.html (read at minimum form "Even if the motherboard supports USB booting, its implementation may be defective, results and direct observation lead to find that there are motherboards with one or more of the following “defects”:" until the end of FAQ #10)
