--- a/src/m/ibmrt.h	Mon Aug 13 11:19:22 2007 +0200
+++ b/src/m/ibmrt.h	Mon Aug 13 11:20:41 2007 +0200
@@ -24,6 +24,11 @@
    operating system this machine is likely to run.
    USUAL-OPSYS="bsd4-2"  */
 
+/* Define WORD_MACHINE if addresses and such have
+ * to be corrected before they can be used as byte counts.  */
+
+#define WORD_MACHINE
+
 /* Now define a symbol for the cpu type, if your compiler
    does not define it automatically.  */
 
@@ -35,6 +40,14 @@
 #define romp /* unfortunately old include files are hanging around.  */
 #endif
 
+/* Define EXPLICIT_SIGN_EXTEND if XINT must explicitly sign-extend
+   the bit field into an int.  In other words, if bit fields
+   are always unsigned.
+
+   If you use NO_UNION_TYPE, this flag does not matter.  */
+
+#define EXPLICIT_SIGN_EXTEND
+
 /* Data type of load average, as read out of kmem.  */
 
 #define LOAD_AVE_TYPE double	/* For AIS (sysV) */
@@ -67,6 +80,11 @@
 
 #define HAVE_ALLOCA
 
+/* The data segment in this machine starts at a fixed address.
+   An address of data cannot be stored correctly in a Lisp object;
+   we always lose the high bits.  We must tell XPNTR to add them back.  */
+
+#define DATA_SEG_BITS 0x10000000
 #define DATA_START    0x10000000
 
 /* The text segment always starts at a fixed address.