diff --git a/common.vhdl b/common.vhdl
index 3cb552d..16ba2b3 100644
--- a/common.vhdl
+++ b/common.vhdl
@@ -75,6 +75,10 @@ package common is
     constant SPR_DEXCRU : spr_num_t := 812;
     constant SPR_HDEXCR : spr_num_t := 471;
     constant SPR_HDEXCU : spr_num_t := 455;
+    constant SPR_NOOP0  : spr_num_t := 808;
+    constant SPR_NOOP1  : spr_num_t := 809;
+    constant SPR_NOOP2  : spr_num_t := 810;
+    constant SPR_NOOP3  : spr_num_t := 811;
 
     -- PMU registers
     constant SPR_UPMC1  : spr_num_t := 771;
@@ -171,6 +175,7 @@ package common is
         ispmu : std_ulogic;
         ronly : std_ulogic;
         wonly : std_ulogic;
+        noop  : std_ulogic;
     end record;
     constant spr_id_init : spr_id := (sel => "0000", others => '0');
 
diff --git a/decode1.vhdl b/decode1.vhdl
index c762b18..1e59725 100644
--- a/decode1.vhdl
+++ b/decode1.vhdl
@@ -457,6 +457,7 @@ architecture behaviour of decode1 is
         i.ispmu := '0';
         i.ronly := '0';
         i.wonly := '0';
+        i.noop  := '0';
         case sprn is
             when SPR_TB =>
                 i.sel := SPRSEL_TB;
@@ -504,6 +505,8 @@ architecture behaviour of decode1 is
             when SPR_DEXCRU | SPR_HDEXCU =>
                 i.sel := SPRSEL_DEXCR;
                 i.ronly := '1';
+            when SPR_NOOP0 | SPR_NOOP1 | SPR_NOOP2 | SPR_NOOP3 =>
+                i.noop := '1';
             when others =>
                 i.valid := '0';
         end case;
diff --git a/decode2.vhdl b/decode2.vhdl
index 1bc8f2b..711f5d8 100644
--- a/decode2.vhdl
+++ b/decode2.vhdl
@@ -696,9 +696,11 @@ begin
             if op = OP_MFSPR then
                 if d_in.ram_spr.valid = '1' then
                     v.e.result_sel := "101";        -- ramspr_result
-                elsif d_in.spr_info.valid = '0' or d_in.spr_info.wonly = '1' then
+                elsif d_in.spr_info.valid = '0' or d_in.spr_info.wonly = '1' or
+                    d_in.spr_info.noop = '1' then
                     -- Privileged mfspr to invalid/unimplemented SPR numbers
                     -- writes the contents of RT back to RT (i.e. it's a no-op)
+                    -- as does any mfspr from the reserved/noop SPR numbers
                     v.e.result_sel := "001";        -- logical_result
                 end if;
             end if;
diff --git a/execute1.vhdl b/execute1.vhdl
index 26f8dae..121d004 100644
--- a/execute1.vhdl
+++ b/execute1.vhdl
@@ -1332,7 +1332,7 @@ begin
             when OP_DARN =>
 	    when OP_MFMSR =>
 	    when OP_MFSPR =>
-		if e_in.spr_is_ram = '1' then
+		if e_in.spr_is_ram = '1' or e_in.spr_select.noop = '1' then
                     if e_in.valid = '1' and not is_X(e_in.insn) then
                         report "MFSPR to SPR " & integer'image(decode_spr_num(e_in.insn)) &
                             "=" & to_hstring(alu_result);