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IBM PC MS-DOS Game Free Conventional Memory Requirements


Free Conventional Memory Requirements



In order to execute, IBM PC MS-DOS games require a certain amount of free conventional memory available. Free conventional memory can also be referred to as low memory, DOS memory or base memory of which there is 640K or 655,360 bytes available. However, MS-DOS and device drivers consume some conventional memory.

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

Available conventional memory can be increased aka "freed up" by disabling Terminate and Stay Resident programs (TSRs) from config.sys and autoexec.bat. Else, "boot disks" can be employed or the PC can be otherwise clean-booted, thereby bypassing the loading of TSRs.

An IBM PC MS-DOS system that does not meet the free conventional memory requirement of a computer game will not be able to run that computer game regardless of how much other RAM it has.

The amount of RAM a game requires depends on its display mode (CGA, EGA, VGA), its audio playback quality (PC Speaker sound effects or digitized sound effects and speech), and various game settings, such as draw detail or distance. For example, a game running in 16K-vRAM CGA may require 384K of free conventional memory whereas the same game running in 256K-vRAM VGA may require 512K.

The 640K RAM barrier was overcome first by memory managers that allowed for high memory allocation (EMS and XMS) and then by DOS Extenders such as Rational Systems' DOS/4GW.

Note that I don't count requirements that disable sound. Also, I count digital sound requirements where applicable. And if a game displays in CGA, EGA or VGA, I count only the VGA requirement.

Format is: Computer Game / Developer / Year / Free conventional memory requirement. 


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