68k instructions timings
Mirroring information from http://oldwww.nvg.ntnu.no/amiga/MC680x0_Sections/mc68000timing.HTML
Effective Address Operand Calculation Timing
This table lists the number of clock periods required to compute an
instruction's effective address. It includes fetching of any extension
words, the address computation , and fetching of the memory operand.
The number of bus read and write cycles is shown in parenthesis as (r/w).
Note there are no write cycles involved in processing the effective address.
Effective Address Calculation Times
register Byte,Word Long
Dn data register direct 0(0/0) 0(0/0)
An address register direct 0(0/0) 0(0/0)
memory
(An) address register indirect 4(1/0) 8(2/0)
(An)+ address register indirect with post- 4(1/0) 8(2/0)
increment
-(An) address register indirect with predec. 6(1/0) 10(2/0)
d(An) address register indirect with dis- 8(2/0) 12(3/0)
placement
d(An,ix) address register indirect with index 10(2/0) 14(3/0)
xxx.W absolute short 8(2/0) 12(3/0)
xxx.L absolute long 12(3/0) 16(4/0)
d(PC) program counter with displacement 8(2/0) 12(3/0)
d(PC,ix) program counter with index 10(2/0) 14(3/0)
#xxx immediate 4(1/0) 8(2/0)
The size of the index register (ix) does not affect execution time
Move Instruction Execution Times
These following two tables indicate the number of clock periods for the move
instruction. This data includes instruction fetch, operand reads, and operand
writes. The number of bus read and write cycles is shown in parenthesis
as (r/w).
Move Byte and Word Instruction Execution Times
Dn An (An) (An)+ -(An) d(An) d(An,ix) xxx.W |xxx.L
Dn 4(1/0) 4(1/0) 8(1/1) 8(1/1) 8(1/1) 12(2/1) 14(2/1) 12(2/1) 16(3/1)
An 4(1/0) 4(1/0) 8(1/1) 8(1/1) 8(1/1) 12(2/1) 14(2/1) 12(2/1) 16(3/1)
(An) 8(2/0) 8(2/0) 12(2/1) 12(2/1) 12(2/1) 16(3/1) 18(3/1) 16(3/1) 20(4/1)
(An)+ 8(2/0) 8(2/0) 12(2/1) 12(2/1) 12(2/1) 16(3/1) 18(3/1) 16(3/1) 20(4/1)
-(An) 10(2/0) 10(2/0) 14(2/1) 14(2/1) 14(2/1) 18(3/1) 20(4/1) 18(3/1) 22(4/1)
d(An) 12(3/0) 12(3/0) 16(3/1) 16(3/1) 16(3/1) 20(4/1) 22(4/1) 20(4/1) 24(5/1)
d(An,ix)14(3/0) 14(3/0) 18(3/1) 18(3/1) 18(3/1) 22(4/1) 24(4/1) 22(4/1) 26(5/1)
xxx.W 12(3/0) 12(3/0) 16(3/1) 16(3/1) 16(3/1) 20(4/1) 22(4/1) 20(4/1) 24(5/1)
xxx.L 16(4/0) 16(4/0) 20(4/1) 20(4/1) 20(4/1) 24(5/1) 26(5/1) 24(5/1) 28(6/1)
d(PC) 12(3/0) 12(3/0) 16(3/1) 16(3/1) 16(3/1) 20(4/1) 22(4/1) 20(4/1) 24(5/1)
d(PC,ix)14(3/0) 14(3/0) 18(3/1) 18(3/1) 18(3/1) 22(4/1) 24(4/1) 22(4/1) 26(5/1)
#xxx 8(2/0) 8(2/0) 12(2/1) 12(2/1) 12(2/1) 16(3/1) 18(3/1) 16(3/1) 20(4/1)
The size of the index register (ix) does not affect execution time
Move Long Instruction Execute Times
Dn An (An) (An)+ -(An) d(An) d(An,ix) xxx.W |xxx.L
Dn 4(1/0) 4(1/0) 12(1/2) 12(1/2) 12(1/2) 16(2/2) 18(2/2) 16(2/2) 20(3/2)
An 4(1/0) 4(1/0) 12(1/2) 12(1/2) 12(1/2) 16(2/2) 18(2/2) 16(2/2) 20(3/2)
(An) 12(3/0) 12(3/0) 20(3/2) 20(3/2) 20(3/2) 24(4/2) 26(4/2) 24(4/2) 28(5/2)
(An)+ 12(3/0) 12(3/0) 20(3/2) 20(3/2) 20(3/2) 24(4/2) 26(4/2) 24(4/2) 28(5/2)
-(An) 14(3/0) 14(3/0) 22(3/2) 22(3/2) 22(3/2) 26(4/2) 28(4/2) 26(4/2) 30(5/2)
d(An) 16(4/0) 16(4/0) 24(4/2) 24(4/2) 24(4/2) 28(5/2) 30(5/2) 28(5/2) 32(6/2)
d(An,ix)18(4/0) 18(4/0) 26(4/2) 26(4/2) 26(4/2) 30(5/2) 32(5/2) 30(5/2) 34(6/2)
xxx.W 16(4/0) 16(4/0) 24(4/2) 24(4/2) 24(4/2) 28(5/2) 30(5/2) 28(5/2) 32(6/2)
xxx.L 20(5/0) 20(5/0) 28(5/2) 28(5/2) 28(5/2) 32(6/2) 34(6/2) 32(6/2) 36(7/2)
d(PC) 16(4/0) 16(4/0) 24(4/2) 24(4/2) 24(4/2) 28(5/2) 30(5/2) 28(5/2) 32(5/2)
d(PC,ix)18(4/0) 18(4/0) 26(4/2) 26(4/2) 26(4/2) 30(5/2) 32(5/2) 30(5/2) 34(6/2)
#xxx 12(3/0) 12(3/0) 20(3/2) 20(3/2) 20(3/2) 24(4/2) 26(4/2) 24(4/2) 28(5/2)
The size of the index register (ix) does not affect execution time
Standard Instruction Execution Times
The number of clock periods shown in this table indicates the time required
to perform the operations, store the results and read the next instruction.
The number of bus read and write cycles is shown in parenthesis as (r/w).
The number of clock periods and the number of read and write cycles must be
added respectively to those of the effective address calculation where
indicated.
In the following table the headings have the following meanings:
An = address register operand, Dn = data register operand, ea = an operand
specified by an effective address, and M = memory effective address operand.
Standard Instruction Execution Times
instruction Size op<ea>,An ^ op<ea>,Dn op Dn,<M>
ADD byte,word 8(1/0) + 4(1/0) + 8(1/1) +
long 6(1/0) +** 6(1/0) +** 12(1/2) +
AND byte,word - 4(1/0) + 8(1/1) +
long - 6(1/0) +** 12(1/2) +
CMP byte,word 6(1/0) + 4(1/0) + -
long 6(1/0) + 6(1/0) + -
DIVS - - 158(1/0) +* -
DIVU - - 140(1/0) +* -
EOR byte,word - 4(1/0) *** 8(1/1) +
long - 8(1/0) *** 12(1/2) +
MULS - - 70(1/0) +* -
MULU - - 70(1/0) +* -
OR byte,word - 4(1/0) +** 8(1/1) +
long - 6(1/0) +** 12(1/2) +
SUB byte,word 8(1/0) + 4(1/0) + 8(1/1) +
long 6(1/0) +** 6(1/0) +** 12(1/2) +
notes: + Add effective address calculation time
^ Word or long only
* Indicates maximum value
** The base time of six clock periods is increased to eight
if the effective address mode is register direct or
immediate (effective address time should also be added)
*** Only available effective address mode is data register direct
DIVS,DIVU - The divide algorithm used by the MC68000 provides less
than 10% difference between the best and the worst case
timings.
MULS,MULU - The multiply algorithm requires 38+2n clocks where
n is defined as:
MULU: n = the number of ones in the <ea>
MULS: n = concatanate the <ea> with a zero as the LSB;
n is the resultant number of 10 or 01 patterns
in the 17-bit source; i.e., worst case happens
when the source is $5555
Immediate Instruction Execution Times
The number of clock periods periods shown in this table includes the time to
fetch immediate operands, perform the operations, store the results and read
the next operation. The number of bus read and write cycles is shown in
parenthesis as (r/w). The number of clock periods and the number of read and
write cycles must be added respectively to those of the effective address
calculation where indicated.
Immediate Instruction Execution Times
instruction size op #,Dn op #,An op #,M
ADDI byte,word 8(2/0) - 12(2/1) +
long 16(3/0) - 20(3/2) +
ADDQ byte,word 4(1/0) 8(1/0) * 8(1/1) +
long 8(1/0) 8(1/0) 12(1/2) +
ANDI byte,word 8(2/0) - 12(2/1) +
long 16(3/0) - 20(3/1) +
CMPI byte,word 8(2/0) - 8(2/0) +
long 14(3/0) - 12(3/0) +
EORI byte,word 8(2/0) - 12(2/1) +
long 16(3/0) - 20(3/2) +
MOVEQ long 4(1/0) - -
ORI byte,word 8(2/0) - 12(2/1) +
long 16(3/0) - 20(3/2) +
SUBI byte,word 8(2/0) - 12(2/1) +
long 16(3/0) - 20(3/2) +
SUBQ byte,word 4(1/0) 8(1/0) * 8(1/1) +
long 8(1/0) 8(1/0) 12(1/2) +
+ Add effective address calculation time
* word only
Single Operand Instruction Execution Times
This table indicates the number of clock periods for the single operand
instructions. The number of bus read and write cycles is shown in parenthesis
as (r/w). The number of clock periods and the number of read and write cycles
must be added respectively to those of the effective address calculation
where indicated.
Single Operand Instruction Execution Times
instruction size register memory
CLR byte,word 4(1/0) 8(1/1) +
long 6(1/0) 12(1/2) +
NBCD byte 6(1/0) 8(1/1) +
NEG byte,word 4(1/0) 8(1/1) +
long 6(1/0) 12(1/2) +
NEGX byte,word 4(1/0) 8(1/1) +
long 6(1/0) 12(1/2) +
NOT byte,word 4(1/0) 8(1/1) +
long 6(1/0) 12(1/2) +
Scc byte,false 4(1/0) 8(1/1) +
byte,true 6(1/0) 8(1/1) +
TAS # byte 4(1/0) 10(1/1) +
TST byte,word 4(1/0) 4(1/0) +
long 4(1/0) 4(1/0) +
+ add effective address calculation time
# This instruction should never be used on the Amiga as its invisiable
read/write cycle can disrupt system DMA.
Rotate Instruction Execution Times
This table indicates the number of clock periods for the shift and rotate
instructions. The number of read and write cycles is shown in parenthesis
as (r/w). The number of clock periods and the number of read and write
cycles must be added respectively to those of the effective address
calculation where indicated.
Shift/Rotate Instruction Execution Times
instruction size register memory
ASR,ASL byte,word 6+2n(1/0) 8(1/1) +
long 8+2n(1/0) -
LSR,LSL byte,word 6+2n(1/0) 8(1/1) +
long 8+2n(1/0) -
ROR,ROL byte,word 6+2n(1/0) 8(1/1) +
long 8+2n(1/0) -
ROXR,ROXl byte,word 6+2n(1/0) 8(1/1) +
long 8+2n(1/0) -
+ add effective address calculation time
n is the shift or rotate count
Bit Manipulation Instruction Execution Times
This table indicates the number of clock periods required for the bit
manipulation instructions. The number of read and write cycles is shown in
parenthesis as (r/w). The number of clock periods and the number of read and
write cycles must be added respectively to those of the effective address
calculation where indicated.
Bit Manipulation Instruction Execution Times
instruction size dynamic static
register memory register memory
BCHG byte - 8(1/1) + - 12(2/1) +
long 8(1/0) * - 12(2/0) * -
BCLR byte - 8(1/1) + - 12(2/1) +
long 10(1/0) * - 14(2/0) * -
BSET byte - 8(1/1) + - 12(2/1) +
long 8(1/0) * - 12(2/0) * -
BTST byte - 4(1/0) + - 8(2/0) +
long 6(1/0) - 10(2/0) -
+ add effective address calculation time
* indicates maximum value
Specificational Instruction Execution Times
This table indicates the number of clock periods for the conditional
instructions. The number of read and write cycles is shown in parenthesis
as (r/w). The number of clock periods and the number of read and write
cycles must be added respectively to those of the effective address
calculation where indicated.
Conditional Instruction Execution Times
instruction displacement branch branch
taken not taken
Bcc byte 10(2/0) 8(1/0)
word 10(2/0) 12(1/0)
BRA byte 10(2/0) -
word 10(2/0) -
BSR byte 18(2/2) -
word 18(2/2) -
DBcc CC true - 12(2/0)
CC false 10(2/0) 14(3/0)
JMP, JSR, LEA, PEA and MOVEM Instruction Execution Times
This Table indicates the number of clock periods required for the jump,
jump-to-subroutine, load effective address, push effective address and
move multiple registers instructions. The number of bus read and write
cycles is shown in parenthesis as (r/w).
JMP, JSR, LEA, PEA and MOVEM Instruction Execution Times
instr size (An) (An)+ -(An) d(An)
JMP - 8(2/0) - - 10(2/0)
JSR - 16(2/2) - - 18(2/2)
LEA - 4(1/0) - - 8(2/0)
PEA - 12(1/2) - - 16(2/2)
MOVEM word 12+4n 12+4n - 16+4n
M->R (3+n/0) (3+n/0) - (4+n/0)
long 12+8n 12+8n - 16+8n
(3+2n/0) (3+2n/0) - (4+2n/0)
MOVEM word 8+4n - 8+4n 12+4n
R->M (2/n) - (2/n) (3/n)
long 8+8n - 8+8n 12+8n
(2/2n) - (2/2n) (3/2n)
instr size d(An,ix)+ xxx.W xxx.L d(PC) d(PC,ix)*
JMP - 14(3/0) 10(2/0) 12(3/0) 10(2/0) 14(3/0)
JSR - 22(2/2) 18(2/2) 20(3/2) 18(2/2) 22(2/2)
LEA - 12(2/0) 8(2/0) 12(3/0) 8(2/0) 12(2/0)
PEA - 20(2/2) 16(2/2) 20(3/2) 16(2/2) 20(2/2)
MOVEM word 18+4n 16+4n 20+4n 16+4n 18+4n
M->R (4+n/0) (4+n/0) (5+n/0) (4+n/0) (4+n/0)
long 18+8n 16+8n 20+8n 16+8n 18+8n
(4+2n/0) (4+2n/0) (5+2n/0) (4+2n/0) (4+2n/0)
MOVEM word 14+4n 12+4n 16+4n - -
R->M (3/n) (3/n) (4/n) - -
long 14+8n 12+8n 16+8n - -
(3/2n) (3/2n) (4/2n) - -
n is the number of registers to move
* is the size of the index register (ix) does not affect the instruction's
execution time
Multi-Precision Instruction Execution Times
This table indicates the number of clock periods for the multi-precision
instructions. The number of clock periods includes the time to fetch both
operands, perform the operations, store the results and read the next
instructions. The number of read and write cycles is shown in parenthesis
as (r/w).
The headings have the following meanings: Dn = data register operand and
M = memory operand.
Multi-Presicion Instruction Execution Times
instruction size op Dn,Dn op M,M
ADDX byte,word 4(1/0) 18(3/1)
long 8(1/0) 30(5/2)
CMPM byte,word - 12(3/0)
long - 20(5/0)
SUBX byte,word 4(1/0) 18(3/1)
long 8(1/0) 30(5/2)
ABCD byte 6(1/0) 18(3/1)
SBCD byte 6(1/0) 18(3/1)
Miscellaneous Instruction Execution Times
This table indicates the number of clock periods for the following
miscellaneous instructions. The number of bus read and write cycles is shown
in parenthesis as (r/w). The number of clock periods and plus the number
of read and write cycles must be added to those of the effective address
calculation where indicated.
Miscellaneous Instruction Execution Times
instruction size register memory
ANDI to CCR byte 20(3/0) -
ANDI to SR word 20(3/0) -
CHK - 10(1/0) + -
EORI to CCR byte 20(3/0) -
EORI to SR word 20(3/0) -
ORI to CCR byte 20(3/0) -
ORI to SR word 20(3/0) -
MOVE from SR - 6(1/0) 8(1/1)+
MOVE to CCR - 12(1/0) 12(1/0)+
MOVE to SR - 12(1/0) 12(1/0)+
EXG - 6(1/0) -
EXT word 4(1/0) -
long 4(1/0) -
LINK - 16(2/2) -
MOVE from USP - 4(1/0) -
MOVE to USP - 4(1/0) -
NOP - 4(1/0) -
RESET - 132(1/0) -
RTE - 20(5/0) -
RTR - 20(5/0) -
RTS - 16(4/0) -
STOP - 4(0/0) -
SWAP - 4(1/0) -
TRAPV (No Trap) - 4(1/0) -
UNLK - 12(3/0) -
+ add effective address calculation time
Move Peripheral Instruction Execution Times
instruction size register->memory memory->register
MOVEP word 16(2/2) 16(4/0)
long 24(2/4) 24(6/0)
Exception Processing Execution Times
This table indicates the number of clock periods for exception processing.
The number of clock periods includes the time for all stacking, the vector
fetch and the fetch of the first two instruction words of the handler routine.
The number of bus read and write cycles is shown in parenthesis as (r/w).
Exception Processing Execution Times
exception periods
address error 50(4/7)
bus error 50(4/7)
CHK instruction (trap taken) 44(5/3)+
Divide by Zero 42(5/3)
illegal instruction 34(4/3)
interrupt 44(5/3)*
privilege violation 34(4/3)
_____
RESET ** 40(6/0)
trace 34(4/3)
TRAP instruction 38(4/3)
TRAPV instruction (trap taken) 34(4/3)
+ add effective address calculation time
* the interrupt acknowledge cycle is assumed to take four
clock periods
_____ ____
** indicates the time from when RESET and HALT are first
sampled as negated to when instruction execution starts