Patching OS/2 for fast machines
From Computer History Wiki
The crash is a division by zero (trap 0) on a DIV CX instruction where the CX register contains zero. The way around this problem is patching OS/2 and getting rid of the bad loop. The original code sequence looks like this: MOV DX, 3 L1: XOR CX, CX L2: LOOP L2 ; loop 65,536 times DEC DX ; run the loop 3 times JNE L1 CLI ... ; read current tick STI SUB CX, BX MOV AX, 1F4h ; 500 MOV BX, 0C8h ; 200 MUL BX ; 500 * 200 = 100,000 DIV CX ; traps if CX = 0 SHR CX, 1 This obviously became a problem as far back as 1991, because OS/2 1.30.1 contains slightly different code: MOV BX, 0C8h ; 200 MUL BX CMP CX, 0 JNE L3 MOV CX, 1Fh ; 31 L3: DIV CX In other words, if CX is zero, it is forced to a non-zero value to avoid the division by zero trap. As it turns out, the MOV/MOV/MUL/DIV instruction sequence is quite unique and occurs only in the BASEDD0x.SYS drivers. To avoid the crash, it is sufficient to remove the DIV instruction, replacing it by NOPs.
It's simple enough to do in HEX.
So basically change this: