.com.unity Forums - Adding a second Hard Drive to a computer

FYI, I pulled this off of www.examnotes.com

There was some discussion on HD size limits, partion limits, and maximum file sizes.

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Here’s the real information on hard drive limitations.
ATA interface Versions up through ATA-5 suffered from a drive capacity limitation of 136.9GB. Depending on the BIOS used, this limitation can be further reduced to 8.4GB, or even as low as 528MB. This is due to limitations in both the BIOS and the ATA interface, which when combined creates even further limitations. You have to look at the BIOS and ATA interface to understand these limits. The BIOS- based driver for hard disks is accessed via software interrupt 13h, which offers functions for reading and writing drives at the sector level.
Starting in 1993-94, most BIOSes began implementing fixes for the problems limiting drive capacity, which enable drives up to the BIOS limit of 8.4GB to be used. This fix involved what is termed parameter translation at the BIOS Setup level, which adapted or translated the cylinder, head, and sector numbers to fit within the allowable BIOS parameters.
Virtually all PC BIOSes since 1994 have translation capability in the BIOS setup, and virtually all offer both CHS translation as well as LBA translation modes. To ensure further development and compatibility, after several revisions in 1996, Phoenix turned over documentation to the National Committee on Information Technology Standards (NCITS) for further enhancement and certification as a standard called the “BIOS Enhanced Disk Drive Specification (EDD). If your system BIOS dates to 1998 or later, you most likely have EDD support, which means support for drives as large as 136.9GB. With the ATA-6 specification in 2001, a new 48-bit address scheme has been designed that extends the limits to 2 ^48 sectors, which is 144.12PB (petabytes). Because the BIOS services allows up to 2^64 sectors, the 144 petabyte limitation will be the lower of the two that will apply. That should hold us for a while.

Operating systems Limitations

1. DOS/Windows 3x – D0S 6.2 or lower cannot support drives greater than 8.4GB. DOS 7.0 or higher (I\included with Windows 95 or later) is required to recognize a drive over 8.4GB.
2. Windows 9X/Me – Windows 95a (original Version) does support the INT13h extensions, which means it does support drives over 8.4GB; however, due to limitations of the FAT16 file system, the maximum individual partition size is limited to 2GB. Windows 95B/OSR2 or later (including Windows 98/ME) supports the INT13h extensions, which allows drives over 8.4GB, and also supports FAT32, which allows partitions sizes up to the maximum capacity of the drive.
3. Window NT – Windows NT 3.5x does not support drive greater than 8.4GB. Windows NT 4.0 does support drives greater than 8.4GB; however, when a drive larger than 8.4GB is being used as the primary bootable device, Windows NT will not recognize more than 8.4GB. Microsoft has released Service Pack 4, which corrects this problem.
4. Window 2000/XP – Windows 2000/XP support drives greater than 8.4GB.
5. OS/2 Warp – Some Versions of OS/2 are limited to a boot partition size of 3.1GB or 4.3GB. IBM has a Device Driver Pack upgrade that enables the boot partition to be as large as 8.4GB. The HPFS files system in OS/2 will support drives up to 64GB.
6. Novell – NetWare 5.0 or later supports drives greater than 8.4GB

FAT16, FAT32 and NTFS 5 size limitations

1. FAT16 – FAT16 uses 16-bits. Supports volumes from 16MB through 2GB by MS-DOS and most Versions of Windows. (Windows NT, Windows 2000, and Windows XP support FAT16 volumes as large as 4GB)
2. FAT32 – FAT32 uses 32-bits. This value is equivalent to 2^28, not 2^32, because 4 bits out of the 32 are reserved for other uses. This expanded value expands the 2GB limit on partition sizes; FAT32 partitions can theoretically be up to 2TB in size (1TB = 1,024GB).
3. NTFS 5 – Because NTFS file offsets are 64 bits long, files and partitions and be up to 16EB (exabytes) in size. (1EB = 2^64 bytes = 17,179,869,184TB)

Now for Microsoft politics. Under Windows 2000 and XP, even though FAT32 supports Volumes from 512MB to 2 TB, the FAT32 volume can only be up to 32GB. Microsoft really wants you to use NTFS which can have volumes larger than 2 Terabytes.

Hope this helps clear up some of the questions on Hard Drive size limitations.[b]

Last edited by Patrickjb on 12-30-02 at 12:56 PM
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also FYI:
http://www.winnetmag.com/Articles/I...?ArticleID=8294