Back in the Days of Windows 95, Moving the Mouse Sped Things Up. This Is How This Trick Worked

Windows 95 was one of Microsoft’s most significant operating systems (OS). It introduced a fully graphical user interface while retaining remnants of MS-DOS.

One notable aspect of its architecture was an asynchronous input/output (I/O) subsystem. When a user or application initiated a file system operation, such as copying files, the OS exhibited curious behavior.

Windows 95 often put tasks to sleep while waiting for file operations to complete. This approach freed up the processor for other applications, rather than wasting cycles repeatedly checking the status of the operation.

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However, as explained years ago on Stack Exchange, limited performance on low-end PCs likely caused Windows 95 to delay processing I/O completion messages. This feature, reportedly inherited from Windows NT, didn’t immediately wake up applications to resume operations. Instead, the system prioritized user input to maintain a smooth and responsive experience.

This behavior led to an unexpected effect: Moving the mouse during file operations sped them up. At the time, experts noted that moving the mouse could reduce the installation time for large applications from an hour to just 15 minutes.

Today, the benefits of moving the mouse to speed up processes are less noticeable, but similar quirks still exist. For instance, when selecting large blocks of text in a browser or editor, quickly moving the mouse at the bottom of the selection can make scrolling faster.

This phenomenon relates to how Windows manages its message queue. Mouse movements generate a stream of messages that keep the system active, causing applications to wake up and respond more frequently.

Microsoft engineer Raymond Chen referenced this behavior in a technical paper, highlighting its roots in OS design. Similarly, developers like Kevin Purcell observed analogous behavior in older systems, such as IBM mainframes and VM/370 terminals. In those systems, pressing the space bar could allocate extra CPU time to speed up programs, including those written in FORTRAN.

Image | Milad Fakurian (Unsplash)

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