diff --git a/cpuid.go b/cpuid.go
deleted file mode 100644
index fbd118f..0000000
--- a/cpuid.go
+++ /dev/null
@@ -1,12 +0,0 @@
-//go:build amd64
-// +build amd64
-
-package unibase2n
-
-func cpuid(op uint32) (eax, ebx, ecx, edx uint32)
-
-// True when SSE2 instructions are available.
-var canusesse2 = func() bool {
-	_, _, c, _ := cpuid(1)
-	return c&(1<<26) > 0
-}()
diff --git a/cpuid_amd64.s b/cpuid_amd64.s
deleted file mode 100644
index 98f50a2..0000000
--- a/cpuid_amd64.s
+++ /dev/null
@@ -1,15 +0,0 @@
-//go:build amd64
-// +build amd64
-
-// Copyright (c) 2015 Klaus Post, released under MIT License. See LICENSE file.
-
-// func cpuid(op uint32) (eax, ebx, ecx, edx uint32)
-TEXT ·cpuid(SB), 7, $0
-    XORQ CX, CX
-    MOVL op+0(FP), AX
-    CPUID
-    MOVL AX, eax+8(FP)
-    MOVL BX, ebx+12(FP)
-    MOVL CX, ecx+16(FP)
-    MOVL DX, edx+20(FP)
-    RET