diff --git a/libsrc/atari/rwcommon.s b/libsrc/atari/rwcommon.s
index afdbb443b..6dd7f14fc 100644
--- a/libsrc/atari/rwcommon.s
+++ b/libsrc/atari/rwcommon.s
@@ -1,53 +1,53 @@
-;
+;				 
 ; common iocb setup routine for read, write
-; expects parameters (int fd,void *buf,int count)
+; expects __fastcall__ parameters (int fd, void *buf, int count)
 ;
-        .include "atari.inc"
-       	.include "errno.inc"
-        .importzp tmp2,tmp3
-        .import incsp6,ldax0sp,ldaxysp
+	.include "atari.inc"
+	.include "errno.inc"
+	.importzp tmp2,tmp3
+	.import incsp4,ldax0sp,ldaxysp
 	.import __errno,__oserror
 	.import	fdtoiocb
 
-        .export __rwsetup
+	.export __rwsetup
 
 __rwsetup:
 
-        ldy     #5
-        jsr     ldaxysp         ; get fd
+	sta	tmp2
+	stx	tmp3		; remember size
+	ldy	#3
+	jsr	ldaxysp		; get fd
 	jsr	fdtoiocb	; convert to iocb
 	bmi	iocberr
-        sta     tmp3            ; save it
-        jsr     ldax0sp         ; get size
-        stx     tmp2
-        ldx     tmp3            ; iocb
+	tax
 	cpx	#$80		; iocb must be 0...7
 	bcs	iocberr
-        sta     ICBLL,x
-        lda     tmp2            ; size hi
-        sta     ICBLH,x
-        ldy     #3              ; get buf addr (was 2 in orig. version)
-        jsr     ldaxysp
-        stx     tmp2
-        ldx     tmp3
-        sta     ICBAL,x
-        lda     tmp2
-        sta     ICBAH,x
-	jsr     incsp6          ; pop args
+	lda	tmp2
+	sta	ICBLL,x
+	lda	tmp3		; size hi
+	sta	ICBLH,x
+	stx	tmp3
+	jsr	ldax0sp		; get buf addr
+	stx	tmp2
+	ldx	tmp3
+	sta	ICBAL,x
+	lda	tmp2
+	sta	ICBAH,x
+	jsr	incsp4		; pop args
 	lda	ICBLL,x
 	ora	ICBLH,x		; return with Z if length was 0
-        rts
+	rts
 
-iocberr:jsr     incsp6          ; pop args
+iocberr:jsr	incsp4		; pop args
 	ldx	#$FF		; indicate error + clear ZF
 	rts
 
 
 ;
 ; this routine updates errno.  do a JMP here right after calling
-; CIOV.  we expect status in Y.
+; CIOV.	 we expect status in Y.
 ;
-        .export __do_oserror,__seterrno,__inviocb
+	.export __do_oserror,__seterrno,__inviocb
 __do_oserror:
 	sty	__oserror	; save os dependent error code
 retminus:
@@ -56,9 +56,9 @@ retminus:
 	rts
 
 __seterrno:
-        sta     __errno
-        stx     __errno+1
-        rts
+	sta	__errno
+	stx	__errno+1
+	rts
 
 ;
 ; sets EINVAL error code and returns -1