diff --git a/transport/internet/kcp/xor.go b/transport/internet/kcp/xor.go
index b9f39f2b..6de9d295 100644
--- a/transport/internet/kcp/xor.go
+++ b/transport/internet/kcp/xor.go
@@ -1,3 +1,5 @@
+// +build !amd64
+
 package kcp
 
 // xorfwd performs XOR forwards in words, x[i] ^= x[i-4], i from 0 to len
diff --git a/transport/internet/kcp/xor_amd64.go b/transport/internet/kcp/xor_amd64.go
new file mode 100644
index 00000000..40d6a1be
--- /dev/null
+++ b/transport/internet/kcp/xor_amd64.go
@@ -0,0 +1,4 @@
+package kcp
+
+func xorfwd(x []byte)
+func xorbkd(x []byte)
diff --git a/transport/internet/kcp/xor_amd64.s b/transport/internet/kcp/xor_amd64.s
new file mode 100644
index 00000000..0c2759d7
--- /dev/null
+++ b/transport/internet/kcp/xor_amd64.s
@@ -0,0 +1,47 @@
+#include "textflag.h"
+
+// func xorfwd(x []byte)
+TEXT ·xorfwd(SB),NOSPLIT,$0
+  MOVQ x+0(FP), SI  // x[i]
+  MOVQ x_len+8(FP), CX  // x.len
+  MOVQ x+0(FP), DI
+  ADDQ $4, DI       // x[i+4]
+  SUBQ $4, CX
+xorfwdloop:
+  MOVL (SI), AX
+  XORL AX, (DI)
+  ADDQ $4, SI
+  ADDQ $4, DI
+  SUBQ $4, CX
+
+  CMPL CX, $0
+  JE xorfwddone
+
+  JMP xorfwdloop
+xorfwddone:        
+  RET
+
+// func xorbkd(x []byte)
+TEXT ·xorbkd(SB),NOSPLIT,$0
+  MOVQ x+0(FP), SI
+  MOVQ x_len+8(FP), CX  // x.len
+  MOVQ x+0(FP), DI
+  ADDQ CX, SI       // x[-8]
+  SUBQ $8, SI
+  ADDQ CX, DI       // x[-4]
+  SUBQ $4, DI
+  SUBQ $4, CX
+xorbkdloop:
+  MOVL (SI), AX
+  XORL AX, (DI)
+  SUBQ $4, SI
+  SUBQ $4, DI
+  SUBQ $4, CX
+
+  CMPL CX, $0
+  JE xorbkddone
+  
+  JMP xorbkdloop
+
+xorbkddone:        
+  RET