How did MS-DOS decide on two seconds to keep the floppy disk cache valid?
10 hours ago
- #Cache
- #MS-DOS
- #Floppy-Disk
- MS-DOS 2.0 had a disk read cache but no disk write cache.
- IBM PC floppy drives lacked lockable doors, allowing disks to be removed at any time.
- The MS-DOS team benchmarked floppy disk swapping speed, setting cache validity to 2 seconds.
- Hardware vendors saved costs by omitting features like door-open detection.
- The 2-second cache policy was crucial for performance on slow floppy disks.
- Modern systems may still reflect this 2-second cache flush policy.
- Different floppy disk sizes (5.25" vs. 3.5") affected swapping speeds.
- MS-DOS later introduced disk IDs to detect disk changes more reliably.