Posted: Tue 07 Sep 2010, 00:44 Post subject:
USB flash drives not detected as boot devices. Why? Subject description: But USB external hard disk drives are.
I want to be able to boot up my laptop from USB flash drives. However, no matter what boot loader I try the laptop does not recognise flash drives as boot devices and just ignores them.
My most recent attempt was the Bootflash script from Wary 70. The Combo format option causes the computer to freeze when I try and run it but the other options run but don't make the flash drives any more detectable.
I have previously tried the Puppy universal installer, Unetbootin and more manual formatting and installing of different bootloaders.
I have read about Plop but I can't seem to understand the point of it. While it raves on a lot about USB booting it looks to me like that is a false description and shouldn't refer to booting at all.
If it is not possible for my laptop to boot from flash drives then okay but I need to understand why it treats USB Hard Disk Drives differently and if there is anything that that indicates about flash drives.
USB bootability varies widely among different machines and BIOS's. I have a fairly recent machine that will only boot from a USB CD-ROM drive.
Since you have tried several techniques to make a bootable flash drive and they all failed, the most likely culprit is your particular machine. You need to find some other machines to include in your testing.
but I need to understand why it treats USB Hard Disk Drives differently
That question can only be answered by the manufacturer of your BIOS.
Sounds like you need to "Flip The Removable Media Bit " to make the flash drive act as a hard drive.
Here is one from Lexor that might work for you
Joined: 12 Aug 2006 Posts: 1406 Location: Tamworth UK
Posted: Sat 11 Sep 2010, 14:36 Post subject:
Flipping the bit does not always work. There are three kinds of USB stick.
1) those that pretend to be hard disks
2) those that pretend to be 'superfloppies' like an iomega zip drive (this is the most common)
3) those that can be flipped between 1) and 2) by changing 1 bit in the controller.
The layout of the boot/partitioning is different between the two
Most BIOS will recognise 2) AND NOT 1)
Some recognise 1) and not 2) which I suspect you have (Thinkpads T4n I know fall into this class)
even less recognise both.
It is possible to confuse the issue and format the drive incorrectly so a type 1) can be formatted as if it was a type 2) and vice versa. This will confuse even BIOSes that normally would recognise either type.
One BIOS that I know looks at the bit and reports the type is the AMI BIOS from an ECS k7S5A Pro which is perhaps why they are so popular.
Tools like FLASHBOOT ask you which type your stick is.
Windows treats the drives differently and reports type 1) as a 'local' disk and allows you to cache writes and partition it whereas type 2) show as a removable drive and it won't cache writes properly or allow partitioning other than as a single partition.
There are drivers for Windows that if used treat type 2) as if they were type 1)
As a IT Consultant I carry one of each type with Puppy+ wine and Hiren plus a load of Portable Aps on. _________________ "Just think of it as leaving early to avoid the rush" - T Pratchett
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