must size a and c correct, too

src/etc/etc.alpha/disktab

@@ -1,4 +1,4 @@
-#	$OpenBSD: disktab,v 1.16 2007/06/16 16:44:42 deraadt Exp $
+#	$OpenBSD: disktab,v 1.17 2007/06/16 18:14:14 deraadt Exp $
 #	$NetBSD: disktab,v 1.2 1995/10/13 03:09:39 cgd Exp $
 
 # A DEC RZ25, configured so that all of the free partition IDs are at
@@ -18,8 +18,8 @@ floppy|floppy3|3in|3.5in High Density Floppy:\
 
 rdroot:\
 	:ty=ramdisk:se#512:nt#2:rm#300:ns#8:nc#359:\
-	:pa#6144:oa#0:ta=4.2BSD:ba#8192:fa#1024: \
-	:pc#6144:oc#0:
+	:pa#5744:oa#0:ta=4.2BSD:ba#8192:fa#1024: \
+	:pc#5744:oc#0:
 
 # test if not having an 'a' works?
 OpenBSD2.1|Fake image for Bootable CDROM:\