Which DOS Version Is The Least Memory Hungry?

Booting Every Single DOS Version & Checking The Free Conventional Memory So You Don’t Have To

I booted every single version of MS-DOS and IBM PC-DOS in VirtualBox using modified images from WinWorld, and ran the chkdsk command to see how much conventional memory was available. These have had their autoexec.bat and config.sys files either deleted or cleared, so there were no TSRs taking up memory in the background.

Note that results under other emulators and on real hardware may vary, but will be relatively the same and in the same ballpark. This is something that I hope to delve into in more detail in future updates to this page.

MS-DOS

Version Bytes Total Bytes Free Bytes Used Notes
3.30 654,336 599,360 54,976  
3.31 654,336 598,384 55,952 Support for HDD partitions over 32MB
4.00 655,360 563,088 92,272  
4.01 655,360 569,296 86,064  
4.01c 655,360 588,464 66,896  
5.00 655,360 583,280 72,080 MS-DOS Editor (EDIT.COM) and QBasic added
5.00a 655,360 583,280 72,080 Bugfix release for the above
6.00 655,360 582,192 73,168 New disk utlities, DoubleSpace disk compression
6.20 655,360 581,472 73,888  
6.21 655,360 581,472 73,888 DoubleSpace removed
6.22 655,360 581,472 73,888 DriveSpace added

IBM PC-DOS

Version Bytes Total Bytes Free Bytes Used Notes
1.00 654,336 642,192 12,144  
1.10 654,336 641,936 12,400 Double sided disk support
2.00 654,336 629,648 24,688 Hard Disk Drives, subdirectories, device drivers
2.10 654,336 629,648 24,688  
3.00 654,336 615,440 38,896 Support for larger disks
3.10 654,336 615,408 38,928 Networking support
3.20 654,336 608,368 45,968 3.5” 720K floppy support
3.30 654,336 599,504 54,832 3.5” 1.44MB floppy support, extended partitions
4.00 655,360 564,656 90,704 DOS Shell, EMS 4.0 support
4.10 655,360 564,640 90,720  
5.00 655,360 583,248 72,112  
5.00.1 655,360 583,232 72,128  
5.02 655,360 581,696 73,664  
6.1 655,360 590,768 64,592 First version after split with MS
6.3 655,360 590,752 64,608 SuperStor Disk Compression added
7.0 655,360 591,568 63,792 Memory optimizations, Stacker disk compression, Rexx
2000 655,360 591,488 63,872  

My Opinion

If you are looking for a “modern” DOS for old machines, with support for large drives and networking but a 3.x-4.x era memory footprint, go for IBM PC-DOS 2000. I run it on my IBM 5150 with 640K of RAM with no issues.

Personally, I would not recommend any version of DOS lower than PC-DOS 3.30 / MS-DOS 3.31 unless you can live with the severe limitations with regard to disk support. I also wouldn’t recommend any version of 4.x, as it is notoriously buggy.

For anything 386-era and above, you may also want to consider the FreeDOS project.

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