diff -r 36ed6d4654bb -r 522a865288d9 src/arch/x86/isa/decoder/x87.isa
--- a/src/arch/x86/isa/decoder/x87.isa	Fri Jan 04 19:00:48 2013 -0600
+++ b/src/arch/x86/isa/decoder/x87.isa	Sat Jan 05 10:14:17 2013 -0600
@@ -68,8 +68,8 @@
             }
             0x4: decode MODRM_MOD {
                 0x3: decode MODRM_RM {
-                    0x0: fchs();
-                    0x1: fabs();
+                    0x0: Inst::FCHS();
+                    0x1: Inst::FABS();
                     0x4: ftst();
                     0x5: fxam();
                     default: Inst::UD2();
diff -r 36ed6d4654bb -r 522a865288d9 src/arch/x86/isa/insts/x87/arithmetic/change_sign.py
--- a/src/arch/x86/isa/insts/x87/arithmetic/change_sign.py	Fri Jan 04 19:00:48 2013 -0600
+++ b/src/arch/x86/isa/insts/x87/arithmetic/change_sign.py	Sat Jan 05 10:14:17 2013 -0600
@@ -36,6 +36,12 @@
 # Authors: Gabe Black
 
 microcode = '''
-# FABS
-# FCHS
+
+def macroop FABS {
+    absfp st(0), st(0)
+};
+
+def macroop FCHS {
+    chsfp st(0), st(0)
+};
 '''
diff -r 36ed6d4654bb -r 522a865288d9 src/arch/x86/isa/microops/fpop.isa
--- a/src/arch/x86/isa/microops/fpop.isa	Fri Jan 04 19:00:48 2013 -0600
+++ b/src/arch/x86/isa/microops/fpop.isa	Sat Jan 05 10:14:17 2013 -0600
@@ -331,4 +331,12 @@
             else if(FpSrcReg1 == FpSrcReg2)
                 ccFlagBits = ccFlagBits | ZFBit;
         '''
+
+    class absfp(FpUnaryOp):
+        code = 'FpDestReg = fabs(FpSrcReg1);'
+        flag_code = 'FSW &= (~CC1Bit);'
+
+    class chsfp(FpUnaryOp):
+        code = 'FpDestReg = (-1) * (FpSrcReg1);'
+        flag_code = 'FSW &= (~CC1Bit);'
 }};
diff -r 36ed6d4654bb -r 522a865288d9 src/arch/x86/isa/operands.isa
--- a/src/arch/x86/isa/operands.isa	Fri Jan 04 19:00:48 2013 -0600
+++ b/src/arch/x86/isa/operands.isa	Sat Jan 05 10:14:17 2013 -0600
@@ -158,7 +158,11 @@
         # These register should needs to be more protected so that later
         # instructions don't map their indexes with an old value.
         'nccFlagBits':   controlReg('MISCREG_RFLAGS', 65),
+
+        # Registers related to the state of x87 floating point unit.
         'TOP':           controlReg('MISCREG_X87_TOP', 66, ctype='ub'),
+        'FSW':           controlReg('MISCREG_FSW', 67, ctype='uw'),
+
         # The segment base as used by memory instructions.
         'SegBase':       controlReg('MISCREG_SEG_EFF_BASE(segment)', 70),
 
diff -r 36ed6d4654bb -r 522a865288d9 src/arch/x86/regs/misc.hh
--- a/src/arch/x86/regs/misc.hh	Fri Jan 04 19:00:48 2013 -0600
+++ b/src/arch/x86/regs/misc.hh	Sat Jan 05 10:14:17 2013 -0600
@@ -79,6 +79,25 @@
         IDBit = 1 << 21
     };
 
+    enum X87StatusBit {
+        // Exception Flags
+        IEBit = 1 << 0,
+        DEBit = 1 << 1,
+        ZEBit = 1 << 2,
+        OEBit = 1 << 3,
+        UEBit = 1 << 4,
+        PEBit = 1 << 5,
+
+        // !Exception Flags
+        StackFaultBit = 1 << 6,
+        ErrSummaryBit = 1 << 7,
+        CC0Bit = 1 << 8,
+        CC1Bit = 1 << 9,
+        CC2Bit = 1 << 10,
+        CC3Bit = 1 << 14,
+        BusyBit = 1 << 15,
+    };
+
     enum MiscRegIndex
     {
         // Control registers