NASM 2.05 based x86 Instruction Reference[ch304]
A.5.280 RSQRTSS: Scalar Single-Precision FP Square Root Reciprocal RSQRTSS xmm1,xmm2/m128 ; F3 0F 52 /r [KATMAI,SSE] RSQRTSS returns an approximation of the reciprocal of the square root of the lowest order single-precision FP value from the source, and stores it in the low doubleword of the destination register. The upper three fields of xmm1 are preserved. The maximum error for this approximation is: |Error| <= 1.5 x 2^-12