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This HTML version of the file intel.doc from the
PC Game Programmer's guide was produced by Zack T Smith. Fancy HTML modifications are copyright ©
2005 by Zack T Smith, all rights reserved.
This information is provided in the hope that it will be useful,
but without any warranty. It is provided AS-IS,
without even the implied warranty of fitness for a particular purpose.
R Instructions
RCL - Rotate Through Carry Left
Usage: RCL dest,count
Modifies flags: CF OF
+-----+-----------------------+
+---| C | 7 <---------------- 0 |<--+
| +-----+-----------------------+ |
| |
+-------------------------------------+
Rotates the bits in the destination to the left "count" times with
all data pushed out the left side re-entering on the right. The
Carry Flag holds the last bit rotated out.
Clocks Size
Operands 808x 286 386 486 Bytes
reg,1 2 2 9 3 2
mem,1 15+EA 7 10 4 2-4 (W88=23+EA)
reg,CL 8+4n 5+n 9 8-30 2
mem,CL 20+EA+4n 8+n 10 9-31 2-4 (W88=28+EA+4n)
reg,immed8 - 5+n 9 8-30 3
mem,immed8 - 8+n 10 9-31 3-5
RCR - Rotate Through Carry Right
Usage: RCR dest,count
Modifies flags: CF OF
+-----------------------+-----+
+-->| 7 ----------------> 0 | C |---+
| +-----------------------+-----+ |
| |
+-------------------------------------+
Rotates the bits in the destination to the right "count" times with
all data pushed out the right side re-entering on the left. The
Carry Flag holds the last bit rotated out.
Clocks Size
Operands 808x 286 386 486 Bytes
reg,1 2 2 9 3 2
mem,1 15+EA 7 10 4 2-4 (W88=23+EA)
reg,CL 8+4n 5+n 9 8-30 2
mem,CL 20+EA+4n 8+n 10 9-31 2-4 (W88=28+EA+4n)
reg,immed8 - 5+n 9 8-30 3
mem,immed8 - 8+n 10 9-31 3-5
REP - Repeat String Operation
Usage: REP
Modifies flags: None
Repeats execution of string instructions while CX != 0. After
each string operation, CX is decremented and the Zero Flag is
tested. The combination of a repeat prefix and a segment override
on CPU's before the 386 may result in errors if an interrupt occurs
before CX=0. The following code shows code that is susceptible to
this and how to avoid it:
again: rep movs byte ptr ES:[DI],ES:[SI] ; vulnerable instr.
jcxz next ; continue if REP successful
loop again ; interrupt goofed count
next:
Clocks Size
Operands 808x 286 386 486 Bytes
none 2 2 2 1
REPE/REPZ - Repeat Equal / Repeat Zero
Usage: REPE
REPZ
Modifies flags: None
Repeats execution of string instructions while CX != 0 and the Zero
Flag is set. CX is decremented and the Zero Flag tested after
each string operation. The combination of a repeat prefix and a
segment override on processors other than the 386 may result in
errors if an interrupt occurs before CX=0.
Clocks Size
Operands 808x 286 386 486 Bytes
none 2 2 2 1
REPNE/REPNZ - Repeat Not Equal / Repeat Not Zero
Usage: REPNE
REPNZ
Modifies flags: None
Repeats execution of string instructions while CX != 0 and the Zero
Flag is clear. CX is decremented and the Zero Flag tested after
each string operation. The combination of a repeat prefix and a
segment override on processors other than the 386 may result in
errors if an interrupt occurs before CX=0.
Clocks Size
Operands 808x 286 386 486 Bytes
none 2 2 2 1
RET/RETF - Return From Procedure
Usage: RET nBytes
RETF nBytes
RETN nBytes
Modifies flags: None
Transfers control from a procedure back to the instruction address
saved on the stack. "n bytes" is an optional number of bytes to
release. Far returns pop the IP followed by the CS, while near
returns pop only the IP register.
Clocks Size
Operands 808x 286 386 486 Bytes
retn 16/20 11+m 10+m 5 1
retn immed 20/24 11+m 10+m 5 3
retf 26/34 15+m 18+m 13 1
retf (PM, same priv.) - 32+m 18 1
retf (PM, lesser priv.) - 68 33 1
retf immed 25/33 15+m 18+m 14 3
retf immed (PM, same priv.) 32+m 17 1
retf immed (PM, lesser priv.) 68 33 1
ROL - Rotate Left
Usage: ROL dest,count
Modifies flags: CF OF
+---+ +-----------------------+
| C |<---+--| 7 <---------------- 0 |<--+
+---+ | +-----------------------+ |
| |
+------------------------------+
Rotates the bits in the destination to the left "count" times with
all data pushed out the left side re-entering on the right. The
Carry Flag will contain the value of the last bit rotated out.
Clocks Size
Operands 808x 286 386 486 Bytes
reg,1 2 2 3 3 2
mem,1 15+EA 7 7 4 2-4 (W88=23+EA)
reg,CL 8+4n 5+n 3 3 2
mem,CL 20+EA+4n 8+n 7 4 2-4 (W88=28+EA+4n)
reg,immed8 - 5+n 3 2 3
mem,immed8 - 8+n 7 4 3-5
ROR - Rotate Right
Usage: ROR dest,count
Modifies flags: CF OF
+-----------------------+ +---+
+-->| 7 ----------------> 0 |---+--->| C |
| +-----------------------+ | +---+
| |
+ ------------------------------+
Rotates the bits in the destination to the right "count" times with
all data pushed out the right side re-entering on the left. The
Carry Flag will contain the value of the last bit rotated out.
Clocks Size
Operands 808x 286 386 486 Bytes
reg,1 2 2 3 3 2
mem,1 15+EA 7 7 4 2-4 (W88=23+EA)
reg,CL 8+4n 5+n 3 3 2
mem,CL 20+EA+4n 8+n 7 4 2-4 (W88=28+EA+4n)
reg,immed8 - 5+n 3 2 3
mem,immed8 - 8+n 7 4 3-5
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