Difference Between MS-DOS 6.20 and MS-DOS 6.22

The primary difference between MS-DOS 6.20 and MS-DOS 6.22 is the disk compression technology included with the operating system. While MS-DOS 6.20 featured Microsoft's integrated disk compression utility known as DoubleSpace, MS-DOS 6.22 replaced it with a newly developed utility called DriveSpace. This transition was the direct result of a major patent infringement lawsuit won by Stac Electronics against Microsoft.

When Microsoft launched MS-DOS 6.0 and subsequently refined it in version 6.20, DoubleSpace was one of the operating system's marquee features. It allowed users to transparently double their hard drive storage capacity on the fly. However, Stac Electronics, the creators of the competing compression software Stacker, sued Microsoft for patent infringement, claiming that DoubleSpace utilized their proprietary data compression algorithms.

In early 1994, a federal court ruled in favor of Stac Electronics, ordering Microsoft to pay damages and recall all versions of MS-DOS containing the infringing DoubleSpace code. In immediate compliance with the court order, Microsoft briefly released MS-DOS 6.21, which simply stripped out DoubleSpace entirely, leaving users without any built-in disk compression tool.

To provide a permanent solution, Microsoft developed a new compression engine that did not violate Stac Electronics' patents. This technology was branded as DriveSpace and released as the centerpiece of MS-DOS 6.22 in June 1994.

Functionally, DriveSpace provided nearly identical capabilities and user interfaces as DoubleSpace, allowing users to create compressed volumes and mount them seamlessly. MS-DOS 6.22 also included conversion utilities so users upgrading from versions 6.0 or 6.20 could convert their existing DoubleSpace compressed volumes into the new DriveSpace format. Aside from the replacement of DoubleSpace with DriveSpace (and the associated utility updates), the core functionality and system files of MS-DOS remained identical between versions 6.20 and 6.22.