For what it is worth, my "take" on 4K-byte (or other-than-512 byte) sectors for DOS systems is very-much the same as Eric's and I shall "reply" to some comments from one of his posts --
> Also depending on your BIOS, you could have a limit of at > most 2^28, 2^32 or 2^48 sectors per disk ... Not a problem for a "driver", as drivers usually assume the programs doing I-O will not try to access PAST the end of a disk! The disk directory controls how much data shall get read/written, and the disk driver "takes its orders" from a DOS system. Absolute disk size is only a problem when specific HARDWARE commands are needed with different sizes. In the SATA/IDE world, there is only 28-bit or 48-bit LBA addressing, and a 48-bit drive can accept 28-bit commands. Thus, in my UIDE driver, I issue 28-bit commands for up to 28-bit addresses, while I issue 48-bitters for larger addresses. Runs fine! > ... There also is a DOS UIDE cache-and-driver. For example > LBACACHE is one of the tools which assumes 512 bytes/sector > and uses only the first 2^32 sectors which is 2 TB for 512 > bytes/sector. As noted above, UIDE (also UIDE2 and UIDEJR) handles 48-bit "LBA" addressing, if any DOS system were ever to give it an Int 13h AH=42h/43h "LBA" block with addresses so large. I depend on the DOS system to determine if this is necessary, as UIDE does physical I-O only, not "logical" directory I-O where the 32-bit directory limit is of concern. Only the 48-bit "LBA" address limit matters to me and my drivers. > By the way - a DRIVER could interface with any disk with > any sector size and then just provide an int13 or int25/26 > interface with 512 byte "sector" size for data transfer to > DOS. For transfers which do not access (aligned) blocks of > 4 kB size, performance will be worse than native, and you > cannot boot from such a disk, but at least this would WORK > and you could even have a driver as part of the boot chain > before DOS is loaded, just as Ontrack / Ezdrive MBR-loaded > drivers which added LBA support to PCs without a LBA BIOS, > decades ago. Making the KERNEL sector size of DOS 4 kB has > the side effect of BUFFERS also being 4 kB each - wasting > 3.5 kB in each buffer when you access a 512 byte / sector > disk with such a kernel. I agree with much of the above. Changing DOS, and all user apps, for any "new" sector size at THIS late date would be a "Cast-Iron BITCH", in my opinion! [U.S. expression for BAD wives/girlfriends, who are usually made of "softer" items!]. For the moment, UIDE supports only 512-byte sectors, same as LBACACHE and almost every other DOS hard-disk driver. But, if "new" 4K-byte sector schemes provide a RELIABLE means for a drive to tell its driver what sector size is in use, I can change UIDE to detect that size! Not-much help for booting or with "independent" programs like FDISK, etc. But, Eric is correct: Changing only the DOS disk driver to accomodate large sector sizes, then letting the driver "interface" with the existing DOS system at 512 bytes/sector, would be a HUGE "simplification" of this entire issue! ------------------------------------------------------------------------------ RSA(R) Conference 2012 Mar 27 - Feb 2 Save $400 by Jan. 27 Register now! http://p.sf.net/sfu/rsa-sfdev2dev2 _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
