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


EMS RAM Requirements



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

The amount of EMS RAM 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 RAM facilitated the likes of digitized sound and square-pixel SVGA display resolutions.

Expanded memory managers (EMMs) include QEMM, 386 MAX and EMM386. Via some EMMs XMS RAM 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 RAM 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 RAM 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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