MS-DOS 3.20 (07-07-1986) doesn't boot on IBM PC 5150 (Rev.1 and Rev.2 BIOS)

[fs5500]

I figured out that MS-DOS 3.20 (07-07-1986) doesn't boot on IBM PC 5150 (BIOS rev.1 -- 04/24/1981 , BIOS rev.2 -- 10/19/1981) with 128KB or higher RAM

But IBM PC-DOS 3.20 (12-30-1985) has no problem on its machine
This problem is only with MS-DOS 3.20 (07-07-1986).

MS-DOS 3.21 (05-01-1987) seems to be fixed this problem.

Anyway, MS-DOS 3.20 (07-07-1986) is only version which doesn't work on IBM PC 5150 rev.1/rev.2

 

[vwestlife]

Probably the version of MS-DOS 3.20 that you have was designed for some specific OEM that used customized hardware, and thus won't run on an original IBM PC. (For example, a copy of MS-DOS for the Tandy 1000 will not boot on an IBM PC.)

Generic, non-OEM-specific versions of MS-DOS were not widely distributed until 3.30.

 

[fs5500]

It is Microsoft MS-DOS 3.20 Genuine (07-07-1986), not from OEM vendor or modified one.
But it is not so issue that most of IBM PC 5150 BIOS is rev.3 (10-27-1982), so there is no problem.
Only the problem is that doesn't work on rev.1 and rev.2 BIOS

If I tested with DOS 3.20 OEM vendor, I would not report this fact.