[IAEP] Anyone gotten a 4GB or greater USB stick to work for Sugar on a Stick?

[Jonas Smedegaard]

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On Thu, Apr 16, 2009 at 09:06:15PM -0400, Caroline Meeks wrote:
>Ahh, this maybe where some of the confusing behavior we were seeing 
>comes from.  Let me repeat what I think I understand so I can see if I 
>have it right.
>
>FAT is the same thing as FAT16
>FAT is only an option for USB sticks 2 GB or less. You can only format 
>a USB stick larger then 2 GB as FAT32.
>Some computers will not boot from a FAT32 formatted stick but some 
>will.
>
>Thus if you put SoaS onto a 4 GB USB it will fail on some computers and 
>not others.
>
>A partition allows you to have one part of the USB formatted 
>differently then another part.
>
>Thus a work around if you want to use a USB stick larger then 2GB would 
>be to create a smaller partition for the boot area and format that as 
>FAT.
>
>Let me know what I have right and wrong!

You got it right.  But there are more works in that can:

FAT is _often_ FAT16. In addition to FAT16 and FAT32 there is also 
FAT12, which some BIOSed might expect in USB-FDD mode.

Also, some BIOSes do not support booting from a USB stick containing 
more than a single partition...:

The various bugs in BIOS implementations apart, there are 3 kinds of 
boot methods for USB storage devices: USB-FDD, USB-HDD and USB-ZIP.

USB-FDD expects no MBR (Master Boot Record), but instead one single 
unpartitioned whole - like a very large floppy disk.

USB-FDD expects an MBR with standard DOS partition table - like a 
harddisk.

USB-ZIP expects an MBR with specific DOS partition table - like a ZIP 
drive.


makebootfat includes a special "mbrfat" combination that makes the 
device look like an unpartitioned single whole to BIOSes expecting 
USB-FDD, while presenting an MBR with a DOS partition table for BIOS-HDD 
use (and possibly BIOS-ZIP too).


I strongly recommend to read the manpage for makebootfat.


I don't know any tools to reverse-engineer boot sectors, which means it 
is not enough to say "yes, it works with makebootfat" - you need to 
document *what* works for *which* machine setup to use *what* USB access 
method.

If you want to approach this systematically, to gain knowledge on what 
hardware supports which combinations of boot methods and tricks, then I 
strongly suggest that you try use makebootfat to prepare the USB sticks, 
or closely read documentation and/or code of other chosen tools to 
understand what exactly they do in comparison.


Kind regards,

  - Jonas

- -- 
* Jonas Smedegaard - idealist og Internet-arkitekt
* Tlf.: +45 40843136  Website: http://dr.jones.dk/

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