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USB 2.0 driver for DOS available - DOSUSB (Announce)

posted by bretjohn Homepage E-mail, Rio Rancho, NM, 29.06.2010, 23:41

> after loading the usbdisk.sys driver you can use int25/int26 (absolute disk
> read/write) to access logical disk sectors of the USB disk. You have to
> define a parameter block here since the partition is >32 MB.
>
> So if you use DOS and not a different OS you can use these interrupts
> instead of int13.
In spite of the fact that DOS calls these functions "absolute disk read & write", the input sector numbers they use are not absolute -- they are relative to the VBR (Volume Boot Record) associated with a specific drive letter. The only way you could use INT 25h/26h to look at or modify the MBR (or other partition records) is if there actually is no MBR or partitions, but only a VBR (i.e., if the disk is formatted as a floppy or "super-floppy"). Some USB disks are in fact formatted as super-floppies, but many aren't.

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