SCSI Controllers and Swap Files Under Windows 3.1

• Microsoft Windows operating system version 3.1, 3.11

Windows version 3.1 uses two types of swap files: permanent and temporary. Windows can use any MS-DOS device that supports file reads and writes as a temporary swap file, including network drives, SCSI hard disks, and floppies. Windows can create permanent swap files only on hard disk devices that support the standard Int 13h interface. Many SCSI controllers support the Int 13h interface, so these devices can support a permanent swap file.

By employing the Windows 32-bit block device driver interface, 32-Bit Disk Access, Windows 3.1 can make better use of a permanent swap file. With 32-Bit Disk Access, paging is faster and MS-DOS programs can be swapped to disk while they are active. The default Windows 3.1 configuration only supports AT-style hard disk controllers based on the Western Digital WD-1003 IDE controller card, so SCSI disks cannot take advantage of the 32-Bit Disk Access features. It is expected that several original equipment manufacturers (OEMs) that manufacture other driver types, including SCSI drives, will be marketing 32-Bit Disk Access block device drivers (VxDs) in the near future.