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IBM PC MS-DOS Game Free Conventional RAM Requirements


Free Conventional RAM Requirements



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

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

Available conventional RAM 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 RAM 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 RAM whereas the same game running in 256K-vRAM VGA may require 512K.

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

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

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


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