add on: Should I limit partitioning for boot partitions on a usb stick for Booting FreeDos to 8 GB? (Or maybe only 512MB or 256MB which are all more than enough to hold the FreeDOS Kernel and OS progs?)
because: > The original BIOS real-mode INT 13h interface supports drives of sizes up to > about 8 GB ( https://en.wikipedia.org/wiki/INT_13H ) > On 31.01.2024, at 10:07, Thomas Cornelius Desi via Freedos-user > <freedos-user@lists.sourceforge.net> wrote: > > I would want to find out if there is any common ground regarding USB Stick > formatting and having access to a second USB Stick when booting FreeDOS from > a first USB Stick. > > Does anyone around know if BIOSes in general differentiate between »floppy > drive« or »hard disk« because of an existing MBR (or partition table) or not? > > Or is this true?: > >> It is also known that a BIOS can treat a 256MB USB drive as a floppy drive, >> but a 512MB USB drive (that contains IDENTICAL contents), as a hard drive >> (the BIOS interrogates the USB drive for it’s physical drive size and from >> the size returned it determines how it should map the drive)." >> > > and / or this: > >> Before a BIOS loads the data (code) from the first sector of a USB drive and >> runs that code, it has to decide how to ‘map’ that device to the standard >> int 13h BIOS call that all boot code uses. > > >> If the BIOS decides that the USB device is a floppy device, the BIOS will >> respond to ‘floppy drive’ int 13h requests (i.e. DL=00). If the BIOS treats >> the device as a hard disk type, it will respond to ‘hard disk’ int 13h >> requests (DL=80h). If the BIOS treats the USB device as a ZIP device, it >> will respond to access requests as a floppy (DL=00) but it will translate >> any request such that a request for Sector 1 (LBA0) will return the PBR of >> the device, a request for Sector 2 will return the sector after the PBR and >> so on. Thus to any real-mode (DOS) OS, the USB ZIP device will appear to be >> just like a big floppy disk with no MBR or reserved sectors. > > > (Quotes from: > https://rmprepusb.com/tutorials/027-diagnose-how-your-bios-boots-usb-drives/#google_vignette > ) > > Thanks if anyone has a knowledge of this info. Is it obsolete/outdated? > > Thomas > > > > _______________________________________________ > Freedos-user mailing list > Freedos-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freedos-user _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
