ML> EV> That AT of his must had been a 286, I guess.   
      
   ML>yes, ATs were introduced with 6mhz 80286 CPUs in them... they also had the   
   ML>16bit ISA bus as compared to the PC and XT 8bit bus... this also worked well   
   ML>with the 286's 16bit design architecture... the AT also came with a 20M HD   
   ML>(compared to the XT's 10M or 20M in later models)... later the brought out t   
   ML>8mhz 80286 with a 30M HD... the AT's 80286 CPU was specifically designed for   
   ML>multitasking but the huge majority of them were sold and used as single user   
   ML>machines... they were "simply" faster DOS boxes to most folks...   
      
   What I rembember form that era was that DOS had a 32 Meg Limit on HD   
   partition size up until Compaq brought out their DOS 3.1 version which   
   broke that barrier.   
   IBM and retained the 32 Meg limit until their later DOS versions.   
      
   Hard disk size limitations in MS-DOS 2.x to MS-DOS 6.22   
   FDISK 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. In MS-DOS 3.0 to   
   MS-DOS 3.2, the limit was raised to 32 MB when FAT16 support was   
   introduced.   
      
   FDISK 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). 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.   
      
   However, in November 1987 Compaq shipped Compaq MS-DOs 3.31 with support   
   for hard disks up to 504 MB. Partitions over 32 MB used the partition   
   type (0x06) which later became present in MS-DOs 4.0 and later.   
      
   FDISK 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).   
      
   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. This bug was due to Microsoft programmers using 32-bit unsigned   
   numbers to store hard disk drive capacity detection in FDISK which would   
   cause the value (in megabytes) to wrap back to zero, meaning that a hard   
   disk larger than 4 GB in capacity will be reported significantly less.   
   IBM's PC-DOS 4.0 only supported partitions of up to 1,024 MB with up to   
   four partitions.   
      
   The 4,095 MB bug was fixed in MS-DOS 5.0 and later where as the capacity   
   limit was raised to 1,024 cylinders, 255 heads and 63 sectors per track   
   for a total of 16,450,560 sectors. At 512 bytes per sector, this totals   
   8,422,686,720 bytes or more commonly - 8,032.5 MB (7.84 GB).   
      
   The hard disk with the maximum capacity of 7.8 GB must be split into   
   four partitions, the 2,047 MB primary partition on drive C would first   
   be created and a Extended DOS partition of 5,977 MB, consisting of two   
   2,047 MB logical partitions on drive D and E and one 1,883 MB partition   
   on drive F.   
      
   If a hard disk has a capacity of 8,032 MB or more, then only 8,032 MB   
   will be usable under MS-DOS 5 and 6.   
      
   Also, when it says "Do you wish to use the maximum available size for a   
   Primary DOS partition?", if you try to select the whole hard disk if the   
   size of the drive is more than 2,047 MB then only the first 2,047 MB   
   will be used and the remaining 5,977 MB will be reserved for a Extended   
   DOS partition.   
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