diff --git a/bochs/cpu/descriptor.h b/bochs/cpu/descriptor.h
index 0ef480dc2..dc3494c82 100755
--- a/bochs/cpu/descriptor.h
+++ b/bochs/cpu/descriptor.h
@@ -1,5 +1,5 @@
 /////////////////////////////////////////////////////////////////////////
-// $Id: descriptor.h,v 1.23 2008-05-13 05:12:11 sshwarts Exp $
+// $Id: descriptor.h,v 1.24 2008-05-26 18:02:07 sshwarts Exp $
 /////////////////////////////////////////////////////////////////////////
 //
 //   Copyright (c) 2007 Stanislav Shwartsman
@@ -23,6 +23,21 @@
 #ifndef BX_DESCRIPTOR_H
 #define BX_DESCRIPTOR_H
 
+//
+// |---------------------------------------------|
+// |             Segment Descriptor              |
+// |---------------------------------------------|
+// |33222222|2|2|2|2| 11 11 |1|11|1|11  |        |
+// |10987654|3|2|1|0| 98 76 |5|43|2|1098|76543210|
+// |--------|-|-|-|-|-------|-|--|-|----|--------|
+// |Base    |G|D|L|A|Limit  |P|D |S|Type|Base    |
+// |[31-24] | |/| |V|[19-16]| |P | |    |[23-16] |
+// |        | |B| |L|       | |L | |    |        |
+// |------------------------|--------------------|
+// |       Base [15-0]      |    Limit [15-0]    |
+// |------------------------|--------------------|
+//
+
 typedef struct { /* bx_selector_t */
   Bit16u value;   /* the 16bit value of the selector */
 #if BX_CPU_LEVEL >= 2
diff --git a/bochs/cpu/io_pro.cc b/bochs/cpu/io_pro.cc
index 554d01794..9e1f78819 100644
--- a/bochs/cpu/io_pro.cc
+++ b/bochs/cpu/io_pro.cc
@@ -1,5 +1,5 @@
 /////////////////////////////////////////////////////////////////////////
-// $Id: io_pro.cc,v 1.32 2008-05-19 20:01:23 sshwarts Exp $
+// $Id: io_pro.cc,v 1.33 2008-05-26 18:02:07 sshwarts Exp $
 /////////////////////////////////////////////////////////////////////////
 //
 //  Copyright (C) 2001  MandrakeSoft S.A.
@@ -133,7 +133,7 @@ bx_bool BX_CPU_C::allow_io(Bit16u addr, unsigned len)
       return(0);
     }
 */
-    if ((Bit32s) (addr/8) >= (Bit32s) (BX_CPU_THIS_PTR tr.cache.u.system.limit_scaled - io_base)) {
+    if ((io_base + addr/8) >= BX_CPU_THIS_PTR tr.cache.u.system.limit_scaled) {
       BX_ERROR(("allow_io(): IO addr %x (len %d) outside TSS IO permission map (base=%x, limit=%x) #GP(0)",
         addr, len, io_base, BX_CPU_THIS_PTR tr.cache.u.system.limit_scaled));
       return(0);