Some information from the Microsoft Knowledge Base: "Windows 95 and MS-DOS use the FDISK utility to partition a disk. When it accesses a hard disk, FDISK uses the system AT ROM BIOS INT13h interface, which has a maximum of 1024 cylinders, 255 heads, and 63 sectors per track. FDISK can access any drive within the limits imposed by the AT ROM BIOS, which means that FDISK can access drives of up to 8 GB, calculated as follows:
1024 cylinders x 255 heads x 63 sectors per track x 512 bytes per sector = 8,422,686,720 bytes, or roughly 8 GB" [That would be your LARGE] "The original IDE hardware interface is limited to 16 heads, which reduces the maximum drive size to 504 MB." [That would be your NORMAL - limited by the original IDE spec (cable signal standard)] "Newer IDE (ATAPI) technology, however, uses a translation scheme called Logical Block Addressing (LBA) to exceed the 504 MB limit as imposed by the system AT ROM BIOS and IDE specification. SCSI and ESDI hard drive controllers use similar translation methods that are usually built into the controller card's ROM BIOS to exceed the 504 MB size limit." [That is your LBA] LBA is, of course, standard nowadays. Basically, with LBA you forget about cylinders, heads, and sectors on a cylinder, and just give the number of the sector on the *disk* (let the disk hardware worry about where it really is). Every IDE disk supports "normal," even the really huge ones, since they have to be backward compatible. Of course, if your OS only supports that, you need to use the disk partitioning software that comes with the disk to get around the limitation, else use only part of your disk. Most also support "large," whereby the disk lies about how many heads it has (called "translation") in order to keep the number of cylinders under 1024. Newer disks all support LBA. Some SurvPC's, of course, have lower limits than even the original "normal" IDE spec. My old 386 BIOS has only predefined drive types, no user-defined type, so I can't install anything bigger than 312MB in it. DOS earlier than 5.0 won't format partitions larger than 32MB (though you could have several - limitation due to maximum cluster size). In DOS 2.x, the limit was even smaller, 20MB I think, though I'm probably wrong on that - and you could only have one partition. Jeffrey L. Hayes [EMAIL PROTECTED] -----Original Message----- From: Charles Angelich [mailto:[EMAIL PROTECTED]] Sent: Friday, August 16, 2002 11:37 AM Subject: Re: What is the difference? CMOS setup. Hello Constant - At 03:42 PM 8/16/02 +0700, you wrote: >If I go into my Cmos setup I find that my hard discs can be >automatically detected. What I do not understand is why >there are three choices possible. >The choice which is highlighted (2) is labeled LBA. >The others are NORMAL and LARGE. >Can somebody tell me what the difference is. >What is the abbreviation LBA? >And why is it highlighted? At http://whatis.techtarget.com/definition/0,,sid9_gci214074,00.html logical block addressing Logical block addressing is a technique that allows a computer to address a hard disk larger than 528 megabytes. A logical block address is a 28-bit value that maps to a specific cylinder-head-sector address on the disk. 28 bits allows sufficient variation to specify addresses on a hard disk up to 8.4 gigabytes in data storage capacity. Logical block addressing is one of the defining features of Enhanced IDE (EIDE), a hard disk interface to the computer bus or data paths. Hope this helps. Charles Angelich The Ghost in the Machine! DOS and W31 Tech website: http://www.undercoverdesign.com/dosghost Stories, poems, music, and photos website: http://www.undercoverdesign.com/dosghost/faf To unsubscribe from SURVPC send a message to [EMAIL PROTECTED] with unsubscribe SURVPC in the body of the message. Also, trim this footer from any quoted replies. More info can be found at; http://www.softcon.com/archives/SURVPC.html
