AMD 250 manual 323, Sfence

25112 Rev. 3.06 September 2005 Software Optimization Guide for AMD64 Processors

Table 18. SSE Instructions (Continued)

		Encoding			Decode
Syntax						FPU pipe(s)	Latency	Note
	Prefix	First	2nd
				ModRM byte	type
	byte	byte	byte
PREFETCHT0 mem8	0Fh	18h		mm-001-xxx	DirectPath	~	~	5
PREFETCHT1 mem8	0Fh	18h		mm-010-xxx	DirectPath	~	~	5
PREFETCHT2 mem8	0Fh	18h		mm-011-xxx	DirectPath	~	~	5
PSADBW mmreg1,	0Fh	F6h		11-xxx-xxx	DirectPath	FADD	3
mmreg2
PSADBW mmreg,	0Fh	F6h		mm-xxx-xxx	DirectPath	FADD	5
mem64
PSHUFW mmreg1,	0Fh	70h			DirectPath	FADD/FMUL	2
mmreg2, imm8
PSHUFW mmreg,	0Fh	70h			DirectPath	FADD/FMUL	4
mem64, imm8
RCPPS xmmreg1,	0Fh	53h		11-xxx-xxx	Double	FMUL	4	1
xmmreg2
RCPPS xmmreg,	0Fh	53h		mm-xxx-xxx	Double	FMUL	6	1
mem128
RCPSS xmmreg1,	F3h	0Fh	53h	11-xxx-xxx	DirectPath	FMUL	3
xmmreg2
RCPSS xmmreg,	F3h	0Fh	53h	mm-xxx-xxx	DirectPath	FMUL	5
mem32
RSQRTPS xmmreg1,	0Fh	52h		11-xxx-xxx	Double	FMUL	4	1
xmmreg2
RSQRTPS xmmreg,	0Fh	52h		mm-xxx-xxx	Double	FMUL	6	1
mem128
RSQRTSS xmmreg1,	F3h	0Fh	52h	11-xxx-xxx	DirectPath	FMUL	3
xmmreg2
RSQRTSS xmmreg,	F3h	0Fh	52h	mm-xxx-xxx	DirectPath	FMUL	5
mem32
SFENCE	0Fh	AEh		11-111-000	VectorPath		2/8	6

Notes:

1. The low half of the result is available one cycle earlier than listed.

2. The second latency value indicates when the low half of the result becomes available.

3. The high half of the result is available one cycle earlier than listed.

4. The latency listed is the absolute minimum, while average latencies may be higher and are a function of internal pipeline conditions.

5. For the PREFETCHNTA/T0/T1/T2 instructions, the mem8 value refers to an address in the 64-byte line to be prefetched.

6. The 8-clock latency is only visible to younger stores that need to do an external write. The 2-clock latency is visible to the other stores and instructions.

7. This is the execution latency for the instruction. The time to complete the external write depends on the memory speed and the hardware implementation.

Appendix C Instruction Latencies 323