x86 Instruction Set Reference

PSRLDQ - Shift Double Quadword Right Logical

Opcode Mnemonic Description
66 0F 73 /3 ib PSRLDQ xmm1, imm8 Shift xmm1 right by imm8 while shifting in 0s.
Description

Shifts the destination operand (first operand) to the right by the number of bytes specified in the count operand (second operand). The empty high-order bytes are cleared (set to all 0s). If the value specified by the count operand is greater than 15, the destination operand is set to all 0s.

The destination operand is an XMM register. The count operand is an 8-bit immediate.
Operation 
Temporary = Count;
if(Temporary > 15) Temporary = 16;
Destination = Destination >> (Temporary * 8);
Flags affected

None.

Instruction Latency Throughput Execution Unit
CPUID0F3n/0F2n/069n0F3n/0F2n/069n0F2n
PSRLDQ xmm, imm84/4/42/2/4MMX_SHFT