on this old comp i got there is a debug mode in BIOS. it gave me the fallowing ASM. can some one make sense of it?
Code:
JMP 065B
MOV DI,0005
MOV BX,7C00
MOV AX,0201
PUSH DI
INT 13
POP DI
JAE 0678
XOR AX,AX
INT 13
DEC DI
JNZ 0660
MOV SI,06A3
JMP 064B
MOV SI,06C2
With the little knowledge i have of ASM, it doesent do anything...?
First command jumps to offset 065B, dunno if it's in the snippet you posted, if it isnt then the code does nothing...
but other then that, it sets some registers, calls interrupt 13 (check it out at ralf brwns interrupt list)
Then I dunno.... does some checks, some conditional jumps, calls int 13 again.... looks weird....
The part you posted reads one sector from the floppy disk and then resets the drive heads.
ok...well i cant figure out how to use the debug to write in asm. it only seems to give out randome code adn display memory segements.
so is that the 'code' used to see if there is a boot disk in the drive?
more fun stuff:
Code:
PUSH AX
MOV AH,78
CALL 5F78
CALL 5F90
TEST AL,26
POP AX
JNZ A449
STI
HLT
JMP A446
CLI
CLD
CS:
MOV DS,[00C6]
PUSHF
CLI
INC BYTE PRT [00CF]
OUT FB,AL
POPF BYTE PRT [00CF],01
MOV CS
PUSH SS
POP SP,0378
MOV AX,0003
INT 10
MOV DX,0000
CALL A2E2
CS:
MOV BYTE PRT [0086],00
PUSH CS
POP ES
MOV DI,0088
MOV CX,001E
XOR AX,AX
REPE
STOSB