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> Main > F7C8B100 show as TEST AX,0x00B1 |
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Tomasz Grysztar 12 Dec 2017, 10:13
Just recently there was a thread where I discussed this. My guess was that this is one of the old contractions of the opcode space preserved for compatibility.
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12 Dec 2017, 10:13 |
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l4m2 12 Dec 2017, 10:26
Code: (8F) 0 POP 1 #UD 2 #UD 3 #UD 4 #UD 5 #UD 6 #UD 7 #UD (FE,FF) 0 INC 1 DEC 2 CALL 3 CALLF 4 JMP 5 JMPF 6 PUSH 7 #UD (D0-D3) 0 ROL 1 ROR 2 RCL 3 RCR 4 SHL 5 SHR 6 SAL 7 SAR (F6,F7) 0 TEST 1 TEST 2 NOT 3 NEG 4 MUL 5 IMUL 6 DIV 7 IDIV |
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12 Dec 2017, 10:26 |
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l4m2 12 Dec 2017, 10:31
Another problem may be hard to answer: Why POP mem is in 8F leaving the rest of 8F empty, while PUSH is in FF and leave FF/7 empty
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12 Dec 2017, 10:31 |
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revolution 12 Dec 2017, 10:38
l4m2 wrote: Another problem may be hard to answer: Why POP mem is in 8F leaving the rest of 8F empty, while PUSH is in FF and leave FF/7 empty There is lots of old crap like that in the x86 encodings. You will be able to find more if you look further. It is an old architecture, it has many warts and scars. Be kind to it, the poor old thing. |
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12 Dec 2017, 10:38 |
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revolution 12 Dec 2017, 10:42
For your viewing pleasure here is another Cyrix instruction, OIO, that messes with the expected encoding:
https://board.flatassembler.net/topic.php?t=4069 |
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12 Dec 2017, 10:42 |
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l4m2 12 Dec 2017, 11:21
Code: 0 1 2 3 4 5 6 7 0 ADDB *,r ADDW *,r ADDB r,* ADDW r,* ADD AL,i ADD AX,i PUSH ES POP ES 8 ORB *,r ORW *,r ORB r,* ORW r,* OR AL,i OR AX,i PUSH CS 10 ADCB *,r ADCW *,r ADCB r,* ADCW r,* ADC AL,i ADC AX,i PUSH SS POP SS 18 SBBB *,r SBBW *,r SBBB r,* SBBW r,* SBB AL,i SBB AX,i PUSH DS POP DS 20 ANDB *,r ANDW *,r ANDB r,* ANDW r,* AND AL,i AND AX,i ES: DAA 28 SUBB *,r SUBW *,r SUBB r,* SUBW r,* SUB AL,i SUB AX,i CS: DAS 30 XORB *,r XORW *,r XORB r,* XORW r,* XOR AL,i XOR AX,i SS: AAA 38 CMPB *,r CMPW *,r CMPB r,* CMPW r,* CMP AL,i CMP AX,i DS: AAS 40 INC AX INC CX INC DX INC BX INC SP INC BP INC SI INC DI 48 DEC AX DEC CX DEC DX DEC BX DEC SP DEC BP DEC SI DEC DI 50 PUSH AX PUSH CX PUSH DX PUSH BX PUSH SP PUSH BP PUSH SI PUSH DI 58 POP AX POP CX POP DX POP BX POP SP POP BP POP SI POP DI 60 PUSHA POPA BOUND rw,md ARPL *,r FS: GS: 16/32data 16/32addr 68 PUSH i IMUL r,*,i PUSH i8 IMUL r,*,i8 INSB INSW OUTSB OUTSW 70 JO JNO JB JNB JZ JNZ JBE JA 78 JS JNS JPE JPO JL JGE JLE JG 80 C0B *,i C0W *,i C0B *,i C0W *,i8 TSTB r,* TSTW r,* XCHB r,* XCHW r,* 88 MOVB *,r MOVW *,r MOVB r,* MOVW r,* MOV *,s LEA r,m MOV s,* X0W * 90 NOP XCH AX,CX XCH AX,DX XCH AX,BX XCH AX,SP XCH AX,BP XCH AX,SI XCH AX,DI 98 CBW CWD CALLFAR WAIT PUSHF POPF SAHF LAHF A0 MOV AL,[i] MOV AX,[i] MOV [i],AL MOV [i],AX MOVSB MOVSW SMPSB CMPSW A8 TEST AL,i TEST AX,i STOSB STOSW LODSB LODSW SCASB SCASW B0 MOV AL,i MOV CL,i MOV DL,i MOV BL,i MOV AH,i MOV CH,i MOV DH,i MOV BH,i B8 MOV AX,i MOV CX,i MOV DX,i MOV BX,i MOV SP,i MOV BP,i MOV SI,i MOV DI,i C0 X2B *,i X2W *,i RET i RET LES r,m LDS r,m MOVB *,i MOVW *,i C8 ENTER LEAVE RETF i RETF INT3 INT i INTO IRET D0 X2B *,1 X2W *,1 X2B *,CL X2W *,CL AAM AAD SALC XLAT D8 (x87 command) E0 LOOPNZ LOOPZ LOOP JCXZ IN AL,i8 IN AX,i8 OUT i8,AL OUT i8,AX E8 CALL JMP JMPF JMPS IN AL,DX IN AX,DX OUT DX,AL OUT DX,AX F0 LOCK REPNE REP(E) HLT CMC X3B *(,i) X3W *(,i) F8 CLC STC CLI STI CLD STD X1B * X1W * |
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12 Dec 2017, 11:21 |
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revolution 12 Dec 2017, 11:39
0xF1 is the ICEBP
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12 Dec 2017, 11:39 |
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Furs 12 Dec 2017, 12:51
l4m2 wrote: Another problem may be hard to answer: Why POP mem is in 8F leaving the rest of 8F empty, while PUSH is in FF and leave FF/7 empty |
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12 Dec 2017, 12:51 |
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l4m2 13 Dec 2017, 18:37
Furs wrote:
8086 is still more complex than 8051 Code: 0 2 3 4 5 6 8 0 NOP LJMP * RR A INC A INC $ INC @R0 INC R0 1 JBC %,& LCALL * RRC A DEC A DEC $ DEC @R0 DEC R0 2 JB %,& RET RL A ADD A,# ADD A,$ ADD A,@R0 ADD A,R0 3 JNB %,& RETI RLC A ADC A,# ADC A,$ ADC A,@R0 ADC A,R0 4 JC %,& ORL $,A ORL $,# ORL A,# ORL A,$ ORL A,@R0 ORL A,R0 5 JNC %,& ANL $,A ANL $,# ANL A,# ANL A,$ ANL A,@R0 ANL A,R0 6 JZ %,& XRL $,A XRL $,# XRL A,# XRL A,$ XRL A,@R0 XRL A,R0 7 JNZ %,& ORL C,% JMP @A+DPTR MOV A,# MOV $,# MOV @R0,# MOV R0,# 8 SJMP & ANL C,% MOVC A,@A+PC DIV AB MOV $,$ MOV $,@R0 MOV $,R0 9 MOV DPTR,## MOV %,C MOVC A,@A+DPTR SBB A,# SBB A,$ SBB A,@R0 SBB A,R0 A ORL C,/% MOV C,% INC DPTR MUL AB MOV @R0,$ MOV R0,$ B ANL C,/% CPL % CPL C CJNE A,#,& CJNE A,$,& CJNE @R0,#,& CJNE R0,#,$ C PUSH $ CLR % CLR C SWAP A XCH A,$ XCH A,@R0 XCH A,R0 D POP $ SETB % SETB C DA A DJNZ $,& XCHD A,@R0 DJNZ R0,& E MOVX A,@DPTR MOVX A,@R0 MOVX A,@R1 CLR A MOV A,$ MOV A,@R0 MOV A,R0 F MOVX @DPTR,A MOVX @R0,A MOVX @R1,A CPL A MOV $,A MOV @R0,A MOV R0,A |
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13 Dec 2017, 18:37 |
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l4m2 14 Dec 2017, 22:55
Code: C:\DOCUME~1\ADMINI~1>debug -a 139D:0100 int 18 139D:0102 int 3 139D:0103 -t AX=0000 BX=0000 CX=0000 DX=0000 SP=FFE8 BP=0000 SI=0000 DI=0000 DS=139D ES=139D SS=139D CS=0210 IP=0C0E NV UP DI PL NZ NA PO NC 0210:0C0E C4C4 LES AX,SP -t C:\DOCUME~1\ADMINI~1> Now that opcode for LES reg,reg is used, it really go confused? |
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14 Dec 2017, 22:55 |
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Furs 15 Dec 2017, 12:55
They should repurpose lea reg, reg to something.
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15 Dec 2017, 12:55 |
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