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IBM PC MS-DOS Game EMS Memory Requirements Expanded Memory Specification


EMS Memory Requirements



Some IBM PC MS-DOS games require a certain amount of EMS memory in order to execute. EMS stands for Expanded Memory Specification. EMS is a form of high memory that is contrasted with 640K conventional memory, which is low memory.

The amount of EMS memory available can be checked via Microsoft Diagnostics (msd) or the chkdsk and mem commands.

Via expansion boards packed with bank-switched DRAM chips, LIM EMS (Lotus, Intel and Microsoft) 3.0 of 1985 supports 4 megs of RAM, LIM EMS 3.2 of 1986 supports 8 megs of RAM and LIM 4.0 of 1987 supports 32 megs of RAM. [1]

Thus, DOS games that adhere to EMS can take advantage of RAM far beyond the 640K limitation imposed by DOS. In some DOS games EMS memory facilitated the likes of digitized sound and SVGA display resolutions.

Expanded memory managers (EMMs) include QEMM, 386 MAX and EMM386. Via some EMMs XMS memory can be converted to EMS RAM.

The EMM386 driver of MS-DOS 5.0 provides only 256 kbytes of EMS RAM by default. Thus, for more demanding RAM-hungry games EMM386 will need to be manually configured in config.sys via:

DEVICE=C:\DOS\EMM386.EXE [RAM in kbytes].

EMS memory requirements for each game are given below. The requirement is not the absolute minimum requirement but rather the minimum requirement that executes all game features (such as digitized speech).

Format is: Computer Game / Developer / Year / EMS memory requirement.


[1]

RAM expansion boards were often stacked. For example, install 4x 2 meg boards jam-packed with 64K-256K DRAM chips in order to get 8 megs of RAM.

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