MS-DOS 4.0x had a serious bug where as if the size of the hard disk is greater than 4,095 MB, the OS would refuse to boot.even from a floppy disk. Partitions over 32 MB used the partition type (0x06) which later became present in MS-DOs 4.0 and later.įDISK from MS-DOS 4 and MS-DOS 4.01 is limited to a partition size of up to 4,095 MB per hard disk split to a 2,047 MB primary partition (drive C) and a 2,039 MB logical partition (drive D). However, in November 1987 Compaq shipped Compaq MS-DOs 3.31 with support for hard disks up to 504 MB. For this instance, drive C as the primary partition and drives D through R would need to be created - 15 32 MB partitions and a 24 MB logical partition on drive R. In MS-DOS 3.0 to MS-DOS 3.2, the limit was raised to 32 MB when FAT16 support was introduced.įDISK from MS-DOS 3.3 allowed partition sizes of up to 32 MB (or 65,535 sectors at 512 bytes per sector) and recognises hard disks of up to 504 MB (1,024 cylinders, 16 heads and 64 sectors per track). Hard disk size limitations in MS-DOS 2.x to MS-DOS 6.22įDISK from MS-DOS 2.x only had FAT12 support with support for single hard disks up to 16 MB at 4,096 bytes per cluster. However, up to around 3.6 GB of system memory will be usuable to the OS. The system memory limit ceiling was raised to 4 GB in MS-DOS 7, MS-DOs 7.1 and MS-DOS 8. If more than 64 MB of system memory is reported to MS-DOs 6.x, then only 64 MB will be usable. 64 MB or 65,536 KB is very common, because MS-DOS 6.x used a unsigned 16-bit value to store the physical amount of memory in kilobytes. MS-DOS 6 through 6.22 include the HIMEM.SYS XMS 3.x driver which raises the system memory ceiling from 16 MB to 64 MB. If the HIMEM.SYS XMS 3.x is used from MS-DOS 6 through MS-DOS 6.22, then the system memory ceiling would be raised from 16 MB to 64 MB. This is the case when those operating systems came out. MS-DOS 4 and 5 include the HIMEM.SYS XMS 2.x driver which will not allow the OS itself to address more than 16 MB of system memory. Some of the information regarding FDISK hard disk limitations is not documented elsewhere. Here's what I found about MS-DOS and here are the fact that I've learned so far.
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