diff --git a/mach/i86/libem/LIST b/mach/i86/libem/LIST
index 79c36416b..42f99f0d0 100644
--- a/mach/i86/libem/LIST
+++ b/mach/i86/libem/LIST
@@ -8,6 +8,8 @@ cmu4.s
 com.s
 csa2.s
 csb2.s
+csa4.s
+csb4.s
 cuu.s
 dup.s
 dvi.s
diff --git a/mach/i86/libem/csa4.s b/mach/i86/libem/csa4.s
new file mode 100644
index 000000000..43157fcec
--- /dev/null
+++ b/mach/i86/libem/csa4.s
@@ -0,0 +1,30 @@
+.sect .text; .sect .rom; .sect .data; .sect .bss
+.define .csa4
+
+.sect .text
+.csa4:
+				! bx, descriptor address
+				! ax, dx: index
+	mov	cx,(bx)         ! default
+	sub     ax,2(bx)
+				! ignore high order word; if non-zero, the
+				! case descriptor would not fit anyway
+	cmp	ax,6(bx)
+	ja	1f
+2:
+	sal     ax,1
+	add	bx,ax
+	mov     bx,10(bx)
+	test    bx,bx
+	jnz     2f
+1:
+	mov	bx,cx
+	test    bx,bx
+	jnz     2f
+.extern ECASE
+.extern .fat
+	mov     ax,ECASE
+	push    ax
+	jmp     .fat
+2:
+	jmp     bx
diff --git a/mach/i86/libem/csb4.s b/mach/i86/libem/csb4.s
new file mode 100644
index 000000000..bdb812f1c
--- /dev/null
+++ b/mach/i86/libem/csb4.s
@@ -0,0 +1,33 @@
+.sect .text; .sect .rom; .sect .data; .sect .bss
+.define .csb4
+
+.sect .text
+.csb4:
+				!bx: descriptor address
+				!ax, dx:  index
+	push	(bx)		! default
+	mov	cx,2(bx)	! count (ignore high order word, the descriptor
+				! would not fit anyway)
+1:
+	add	bx,6
+	dec     cx
+	jl      4f
+	cmp     ax,(bx)
+	jne     1b
+	cmp	dx,2(bx)
+	jne     1b
+	pop	bx
+	mov	bx,4(bx)
+2:
+	test    bx,bx
+	jnz     3f
+.extern ECASE
+.extern .fat
+	mov     ax,ECASE
+	push    ax
+	jmp     .fat
+3:
+	jmp	bx
+4:
+	pop	bx
+	jmp	2b