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FAT32: The Big Deal About Big Disks
Make that multigig hard drive more manageable.

-- by Lenny Bailes

So you just got a new PC with a hard drive the size of Miami. Now all your storage problems are over, right? Not quite. A bigger disk means larger clusters, and larger clusters mean less efficient use of all that space.

Microsoft's new File Allocation Table file system is designed to make these large drives more manageable by blasting large clusters into byte-sized pieces. If you bought a PC with a hard disk of 2GB or larger this year, odds are it's running the OEM Service Release 2 (SR2) version of Windows 95, which includes this new file system, dubbed FAT32. You'll probably consider FAT32 a blessing if you've already wrestled with a multigigabyte hard drive under Win95. But the new file system causes a number of compatibility problems that make it a mixed blessing at best.

The traditional FAT system (we'll call it FAT16) in Win95 can cope with only 2GB in a single partition. FAT32 lets Win95 manage a single large partition of up to 2 terabytes (2048GB). Better yet, FAT32 uses smaller clusters than FAT16, so you can use that mammoth hard disk more efficiently.

So far, so good. But there's a catch: To use FAT32, you have to upgrade your disk utilities and antivirus software to compatible versions. Some older apps, including Microsoft Office 95 and Office 4.3, may not install properly under SR2. What's more, FAT32 disk partitions created under SR2 can't be seen under older versions of DOS, Windows 95 "Classic" or Windows NT. And SR2 abolishes the popular F4 dual-boot feature, even if you stick to pre-FAT32 partitions.

Clearly, you need to approach FAT32 intelligently. Here's everything you need to know about how it works and how to make the most of it.

Officially scheduled for inclusion in the next edition of Windows, SR2 began shipping in October 1996 and has already shipped on many new PCs. Some hardware and motherboard vendors have purchased OEM licenses from Microsoft to bundle the package with their equipment. If you're not sure whether you're running the SR2 version of Windows 95 with or without the FAT32 file system, here's how to find out.

Right-click on My Computer and select Properties (see The Explorer, July, and our Web site, for more ways to tell which version of Windows you're running). If you're running SR2, you'll see Microsoft Windows 95 4.00.950 B listed in the System area.

To verify the file system of a specific disk partition, select its drive icon in My Computer and right-click on Properties. You'll see either "FAT" or "FAT32" in the disk type description.

How Does FAT32 Work?

In addition to supporting larger drives, FAT32 banishes the cumbersome, cluster-consuming behavior of the FAT16 file system. Under FAT16, a disk partition of 1GB to 2GB requires a cluster size of 32KB. So a simple 1KB document may be allocated as much as 32KB on the hard drive. Any file that exceeds a 32KB multiple by even 1 byte will waste the rest of the next 32KB cluster. Multiply that times many files, and it can eat up a lot of disk space. FAT32 solves this problem by reducing to 4KB the default file cluster size for partitions between 260MB and 8GB. (Drives or partitions under 260MB use .5KB clusters.) Up to 16GB, FAT32's cluster size is 8KB; to 32GB, it's 16KB; and for partitions of 32GB and greater, the cluster size holds steady at 32KB.

FAT32 adds a few other improvements. The root directory on a FAT32 drive is now an ordinary cluster chain, so it can be located anywhere on the drive. This removes FAT16's previous limitation of 512 root directory entries. In addition, the boot record on FAT32 drives has been expanded to allow a backup of critical data structures. This makes FAT32 drives less susceptible to failure.

If you didn't get SR2 bundled with your new PC but rather with a new motherboard or hard drive, there are a few things you should know:

  • Installing SR2 on a brand-name PC or laptop that didn't ship with it may invalidate your technical support contract. Microsoft or your system vendor may not be able to provide you with phone support, and your warranty may not cover restoration/recovery services if your system becomes corrupted.
  • SR2 isn't programmed to upgrade previously installed versions of Windows 3.x or Win95. Generally, it will refuse to install unless you begin with a blank hard disk.
  • To use the FAT32 file system on an IDE drive, your motherboard or disk controller's BIOS must fully support logical block addressing (LBA) mode extensions for drives larger than 1024 cylinders (512MB). The upper limit for a single partition under most SCSI configurations is 8GB. For partitions larger than 8GB on an IDE or SCSI drive, the BIOS must support INT 13 extensions.

Compatibility Considerations

Aside from these special cases, there are a number of compatibility issues that concern all users of FAT32. For one thing, SR2 removes the F4 dual-boot feature of Windows 95 "Classic." Even if you've installed (or reinstalled) SR2 on a FAT16 disk partition, you can't simply press F4 (or select Previous Operating System from the F8 Boot menu) to switch to a previous version of DOS. If you do, the system will boot an old version of DOS once and lock up completely on all subsequent boots until you manually restore the SR2 system files to the hard disk.

FAT32 partitions are also invisible to other operating systems, including other versions of Windows. To access a FAT32 partition from a boot floppy, you must create an SR2 start-up disk. You won't see your C: drive if you boot from an older Win95 or DOS start-up disk. If you start out with SR2 on a FAT32 partition and subsequently install Windows NT or OS/2, neither OS will be able to access the FAT32 partition. (See the sidebar "Boot-Polishing Tips".)

In addition, you can't run disk-compression software (such as Microsoft's DriveSpace) on a FAT32 partition. But it is possible to include both FAT32 and FAT16 partitions on a single hard disk and use DriveSpace compression on FAT16 partitions. (SR2 includes the same DriveSpace 3 compression Microsoft ships with its Plus pack.)

You may also run into problems installing an older Windows application. If you're using the original version of Microsoft Office 95 Standard Edition, you may need to upgrade to Office 95 Professional or obtain a patch to install this software on a FAT32 partition. In addition, Microsoft Office 4.3 (the last 16-bit/Windows 3.1x version) may refuse to install under SR2 because of a revised treatment of the old SHARE.EXE file-locking utility. One workaround for this problem: If Office 4.3 complains it can't find SHARE.EXE, you may choose any small DOS utility or dummy program, rename it SHARE.EXE and temporarily insert it into your AUTOEXEC.BAT. This will allow Office 4.3 to install. You can remove the dummy program from AUTOEXEC.BAT once installation is complete.

Some utilities will present problems as well. If you're using FAT32 disk partitions, you must upgrade your disk-maintenance and antivirus utilities to FAT32-compatible versions. Microsoft's bundled System Tools (ScanDisk and Disk Defragmenter) are FAT32-compliant, but older versions of Norton Utilities and various antivirus packages aren't. (Symantec's 2.0 versions of Norton Utilities and Norton AntiVirus for Windows 95, and IBM's AntiVirus 2.52 are FAT32-compliant and currently shipping.)

Additional compatibility issues may cause problems with early versions of Adaptec's EZ-SCSI software, Quarterdeck's QEMM 8.01, Microsoft's own EMM386.EXE expanded memory manager, IBM Client Access and applications compiled with Borland's 16-bit C compiler.

FAT32 also presents some secondary compatibility issues. SR2's internal Windows 95 Explorer, Defrag and ScanDisk programs have been modified to take advantage of a new API call that correctly reports disk usage on large partitions. But most current third-party applications and setup programs will now report incorrect disk usage numbers on any partition larger than 2GB.

How Do You Work with FAT32?

If all this talk about compatibility hasn't scared you, you're ready to start working with FAT32. If your hardware supports FAT32, you can preinstall a FAT32 partition of at least 512MB on a hard disk by creating an SR2 start-up disk from the SR2 CD-ROM and running FDISK. To create the start-up disk, start the installation of SR2 from the CD-ROM onto a blank partition. When the installation routine prompts you to make a start-up disk, answer "Yes" and insert a diskette into the A: drive. Once you've made the start-up disk, you can cancel the remainder of the Win95 installation. Then boot from the start-up floppy and run FDISK. When prompted to enable large disk support, answer "Yes."

If you have the SR2 CD-ROM and a machine already running Win95 "Classic," you can create an SR2 start-up disk by selecting Control Panel, then Add/Remove Programs. Select the Startup Disk tab and click on Create Disk. When prompted to insert the Windows 95 CD-ROM into your CD-ROM drive, insert the SR2 CD-ROM.

To run your copy of SR2 in conjunction with DOS/Windows 3.x or other operating systems, install it into a FAT16 partition on drive C: rather than into a FAT32 partition. (If your system is already formatted for FAT32, PowerQuest's PartitionMagic 3.03 can reconvert any partition to FAT16 without losing your data. See the sidebar "Boot-Polishing Tips" for details.)

You can restore an approximation of the DOS dual-boot feature to a computer running SR2 as follows:

  • Make sure the old DOS system files and start-up files are present on a FAT16 C: drive, or restore them. Copy COMMAND.COM, IO.SYS and MSDOS.SYS from a DOS boot floppy to IO.DOS, MSDOS.DOS and COMMAND.DOS in the root directory of C:, and enter BootMulti=1 in MSDOS.SYS in the root of C:
  • If you want to dual boot between SR2 on a FAT32 partition and DOS 6 on a FAT16 partition, you must create and install the SR2 partition as drive D: or greater. If you want to dual boot between DOS and SR2 on a shared FAT16 partition, everything can be on the C: drive.
  • After modifying MSDOS.SYS in the root of drive C: to include the BootMulti=1 option, press F4 to start the system with the old version of DOS.

The problem with SR2 is this locks up the Win95/SR2 boot files. The next time you start the system, nothing will boot from the C: drive. To avoid that problem, create and run the following batch file from drive C: under DOS 6.x before you shut down your DOS session.














Press Ctrl+Alt+Delete, and the system will reboot into SR2. Anytime you F4-boot into DOS, run BOOT95.BAT before shutting down to restore the Win95 boot files.

Tech support types and program developers can employ variations of this procedure to dual boot Win95 "Classic" (installed on FAT16 drive C:) with SR2 (installed on FAT16 or FAT32 drive D:) or Windows NT installed on a subsequent FAT16 or NTFS partition.

Once you get beyond all the caveats and compatibility issues, you may find FAT32 hasn't changed your life much. Microsoft says FAT32 uses disk space 10 to 15 percent more efficiently than its predecessor. That may not seem like much now, but you're likely to notice more as hard drives inch ever closer to the inconceivable 2-terabyte mark in the not-so-distant future.

If you must have partitions larger than those allowed by FAT16, you'll probably want to explore the world of FAT32. If not, you might want to stick with those larger FAT16 clusters for the time being.

Lenny Bailes is a San Francisco-based instructor and consultant, and the author of Byte Guide to Optimizing Windows 95 (Osborne McGraw-Hill, 1996). Contact him care of the editor at the addresses on page 20.

Hard Drive Prices Take a Dive

Hard drive prices are falling at a rate of 50 percent per year. And the free fall is expected to continue at this rate for at least the next three to five years, thanks to advances in two technologies: areal density and MR (magnetoresistive) read head.

Areal density refers to the amount of information that can fit into a given area of disk surface. Areal density has increased at an average of 60 percent per year since 1990. The newest hard drives achieve areal densities of approximately 600Mb to 700Mb per square inch, up from 200Mb per square inch only a year or two ago. By the year 2000, expect these densities to reach 10Gb per square inch. MR read heads separate reading and writing into two separate functions and use two permeable magnetic shields to focus the magnetic energy.

Put these two technologies together with manufacturing improvements, and today's average 3.5-inch hard drive of 1.6GB becomes a 12GB drive in the year 2000 at roughly the same price. By then, we can also expect a new class of watch-sized 1GB drives, so cheap and plentiful they can be attached by the dozen to printed circuit boards-resulting in reduced cost and higher reliability.-Jonathan Blackwood

Boot-Polishing Tips

Sweet 16? Or a more mature 32? If you can't decide which way to go, consider V Communications' System Commander or PowerQuest Corp.'s PartitionMagic. These third-party tools let you create and administer multiboot partition configurations with Windows 95 SR2.

System Commander replaces the boot sector on a FAT16 or FAT32 C: drive with its own smart boot menu that automatically recognizes other operating systems as you install them. Each time you start your computer, the System Commander boot menu lets you choose the OS you want to start, automatically shuffling the correct boot-kernel and configuration files to launch it.

The best strategy for using System Commander to set up a multiboot DOS/Win95 SR2 or Win95 "Classic"/Win95 SR2 system is to install each OS on its own primary partition and establish a common extended FAT16 data partition that all the operating systems can see. Because the FDISK utility Microsoft includes with its products doesn't normally permit you to do this, you have to use System Commander's SCDISK utility to hide the first primary partition, freeing FDISK to create a new one:

  • Create and format the first primary partition (FAT16 or FAT32). You may need to create an SR2 start-up boot disk.
  • Install System Commander before you install the OS (other than DOS COMMAND.COM)
  • Install the OS that will be booted from the first partition.
  • Create a boot floppy for the second OS.
  • Use SCDISK to hide the first primary partition. Use the boot disk from the second OS and its partitioning utility to start up your computer and create a new primary partition. Install the second OS, and System Commander will automatically recognize it and add it to the start-up Boot Menu.
  • To store data recognized by both operating systems, use DOS/Win95's FDISK to create an extended FAT16 partition that follows the two primary boot partitions.

If your computer already contains an OS that fills the entire disk, PartitionMagic 3.0 may be the tool you need. It can dynamically shrink and expand existing partitions without losing data, so you can create and format new partitions in FAT16, FAT32, NTFS and HPFS formats. PartitionMagic also includes a bidirectional FAT16-to-FAT32 conversion utility and two runtime boot menu utilities.

IMPORTANT: If you plan to work with FAT32, upgrade to PartitionMagic 3.03 and System Commander 3.06. The version 3 releases of these products both have FAT32-related problems.

If you have a computer with a previously installed OS, follow these steps:

  • Install PartitionMagic in the same partition as the current OS and shrink the current partition to make room for a new OS. (If your first OS is Windows NT on an NTFS partition, copy the PQMAGICT.EXE file from the \PQMAGIC directory to a diskette, boot from a DOS/Win95 boot disk and run PQMAGICT from the A: drive.)
  • Once you've cleared room at the back of the disk, boot your original OS and run PartitionMagic to create and format new primary partitions. Run the PQBOOT utility to make one of the new partitions active, reboot the machine and install the new OS.
  • To share data and applications between operating systems, use PartitionMagic to create an extended FAT16 partition that follows the OS partitions.
  • To return to the original OS, run PQBOOT again to switch the active partition.
  • If you aren't using FAT32, you may install and use the IBM Boot Manager to create a start-up boot menu instead of switching operating systems with PQBOOT.

PartitionMagic 3.03 includes a utility that can move currently installed apps from one partition to another (automatically updating the Win3.1x or Win95 system files), and a second utility that can duplicate an entire partition in empty disk space. These utilities may be useful in setting up multiple instances of Win95 "Classic" or SR2.-Lenny Bailes

Windows Magazine, August 1997, page 223.

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