The controller chip has some internal firmware that basically controls:Ħ) Number of LUN's (only on some chips, there can be a stick seen as two devices)ħ) Type of device (floppy, zip drive, HD, CD)ĩ) Write protection of one of the two LUN's if multiLUNġ0) Type and amount of memory chips connected Often a floppy or hard disk is expected at USB massstorage.Īny USB stick has two main components, controller chip and actual memory chips. Some BIOS may even boot a UDF or CDFS file system from USB massstorage. One USB stick may boot at one machine, but fail at another machine. Remember, there is no USB boot specification.ĭifferent manufacturer created different solutions. The BIOS may boot a fake CD-ROM (U3 CD part). However that's not part of Bootable CD Specification, hence it's not supported officially.
A CD boot is reliable nowadays.īIOS and boot CD follow this specification.Ī current BIOS should boot a USB CD-ROM too. A CD drive dosn't know a file system.ĭifferent hardware and software manufacturer follow this specification. So when a DVD or CD is read in the BIOS is the driver for reading UDF and CDFS contained in the CD drive?No, the BIOS contain a basic CD driver.
