lisämuisti

Lisämuisti is a Finnish term that translates to "additional memory" or "extended memory." In a computing context, it refers to memory that extends beyond the conventional 640 KB limit of early IBM PC architectures. This concept became particularly relevant in the 1980s and early 1990s as software demanded more memory than the standard configuration could provide.

There were several technical approaches to implementing lisämuisti. One prominent method was the Expanded Memory Specification (EMS), developed by Lotus, Intel, and Microsoft. EMS allowed programs to access memory beyond the initial 640 KB through a technique called "bank switching," where portions of the additional memory were swapped in and out of a small window in the conventional memory space. Another approach was Extended Memory Specification (XMS), which provided a more direct way to access memory above 1 megabyte on systems with Intel 80286 or later processors. XMS allowed programs to manage this memory more freely, especially in multitasking environments.

The need for lisämuisti arose due to the limitations of the original IBM PC's memory architecture, which allocated specific address ranges for hardware devices, leaving less than the full 1 megabyte for RAM. As operating systems and applications grew more sophisticated, this limitation became a bottleneck, hindering performance and preventing the execution of larger programs. The introduction of lisämuisti solutions enabled users to run more demanding software and improved overall system responsiveness.