32-bit Disk Access (also known as ''FastDisk'') refers to a special disk access and caching mode available in older,

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...

-based

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

operating systems. It was a set of

protected mode In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as Memory_segmentation, segmentation, virtual mem ...

device driver In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabli ...

s that worked together to take advantage of advanced disk I/O features in the system BIOS. It filtered interrupt 13h

BIOS call BIOS implementations provide interrupts that can be invoked by operating systems and application programs to use the facilities of the firmware on IBM PC compatible computers. Traditionally, BIOS calls are mainly used by DOS programs and some ot ...

s to the

disk controller A disk controller is a controller circuit that enables a CPU to communicate with a hard disk, floppy disk or other kind of disk drive. It also provides an interface between the disk drive and the bus connecting it to the rest of the system.{ ...

and directed them in the most efficient way for the system — either through the 32-bit interface with the hard disk controller or through the system BIOS. Using 32-bit Disk Access allowed for more pageable memory in Windows to page MS-DOS–based applications to disk to free enough RAM for applications when they needed to use it. Sometimes enabling this mode would break older applications of the day. Windows 3.1 had an option in its ''386 Enhanced'' Control Panel that would enable 32-bit read & write access in 386 enhanced mode. Usually, 32-bit read could be safely enabled, but 32-bit write had issues with a number of applications. 32-bit Disk Access was the feature that made it possible to page MS-DOS applications to disk. Without it, if the real mode disk code (the Int 13h handler) was paged out, the virtual DOS machine would loop forever. 32-bit disk access should not be confused with 32-bit file access. Although both technologies are similar, 32-bit disk access was introduced with Windows 3.1 and file access with

Windows for Workgroups Windows 3.1 is a major release of Microsoft Windows. It was released to manufacturing on April 6, 1992, as a successor to Windows 3.0. Like its predecessors, the Windows 3.1 series run as a Shell (computing), shell on top of MS-DOS; it was t ...

3.11. 32-bit file access provided a 32-bit code path for Windows to directly access the disk bus by intercepting the

Int 21H services while remaining in 386

and at CPU speeds, rather than handling the Int 21H services in real mode by MS-DOS. 32-bit disk access offers less performance and is less likely to work on many computers than ''32-bit file access''. ''32-bit file access'' does not require 32-bit disk access.

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...

Windows 98 Windows 98 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It was the second operating system in the 9x line, as the successor to Windows 95. It was Software ...

, and

Windows Me Windows Me (Millennium Edition) is an operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It was the successor to Windows 98, and was released to manufacturing on June 19, 2000, and t ...

use native,

32-bit disk drivers during normal operation. However

Safe Mode Safe mode is a diagnosis, diagnostic mode of a computer operating system (OS). It can also refer to a mode of operation by application software. ''Safe mode'' is intended to help fix most, if not all, problems within an operating system. It is a ...

uses MS-DOS real mode disk drivers instead. Real mode MS-DOS drivers could also be used during normal operation for disk peripherals for which Windows did not have native drivers. 32-bit versions of the

Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...

family of operating systems including the newer

Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft, targeting the server and business markets. It is the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RT ...

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...

Windows Server 2003 Windows Server 2003, codenamed "Whistler Server", is the sixth major version of the Windows NT operating system produced by Microsoft and the first server version to be released under the Windows Server brand name. It is part of the Windows NT ...

Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...

and later always have 32-bit disk drivers active, cannot use MS-DOS drivers at all, and the expression is not used for them.

References

Explanation of SMARTDRV & 32-bit disk access from Microsoft

32-bit in Windows 3.1 / 9x
* https://web.archive.org/web/20070324064925/http://pclt.cis.yale.edu/pclt/OPSYS/WFWG311.HTM

References

Further reading