diff --git a/src_Core/RISCY_OOO/procs/lib/Decode.bsv b/src_Core/RISCY_OOO/procs/lib/Decode.bsv
index 321ff67..f8e5f59 100755
--- a/src_Core/RISCY_OOO/procs/lib/Decode.bsv
+++ b/src_Core/RISCY_OOO/procs/lib/Decode.bsv
@@ -1128,13 +1128,11 @@ function DecodeResult decode(Instruction inst, Bool cap_mode);
                             dInst.capFunc = CapModify (Unseal (Src1));
                         end
                         f7_cap_CTestSubset: begin
-                            illegalInst = True;
-                            // TODO
                             dInst.iType = Cap;
                             regs.dst = Valid(tagged Gpr rd);
-                            regs.src1 = Valid(tagged Gpr rs1);
-                            regs.src2 = Valid(tagged Gpr rs2);
-                            dInst.imm = Invalid;
+                            regs.src1 = Valid(tagged Gpr rs2);
+                            regs.src2 = rs1 == 0 ? Invalid : Valid(tagged Gpr rs1);
+                            dInst.scr = rs1 == 0 ? Valid (SCR_DDC) : Invalid;
                             dInst.capFunc = CapInspect (TestSubset);
                         end
                         f7_cap_CCopyType: begin
diff --git a/src_Core/RISCY_OOO/procs/lib/Exec.bsv b/src_Core/RISCY_OOO/procs/lib/Exec.bsv
index d40cae8..fb2e16b 100755
--- a/src_Core/RISCY_OOO/procs/lib/Exec.bsv
+++ b/src_Core/RISCY_OOO/procs/lib/Exec.bsv
@@ -230,8 +230,12 @@ endfunction
 (* noinline *)
 function Data capInspect(CapPipe a, CapPipe b, CapInspectFunc func);
     Data res = (case(func) matches
-               //tagged TestSubset             :
-               //   error("TestSubset not yet implemented");
+               tagged TestSubset             :
+                   // TODO will be bad for timing. Would like to reuse bounds check
+                   zeroExtend(pack(   (isValidCap(b) == isValidCap(a))
+                                   && ((getPerms(a) & getPerms(b)) == getPerms(a))
+                                   && (getBase(a) >= getBase(b))
+                                   && (getTop(a) >= getTop(b))));
                tagged GetLen                 :
                    truncate(getLength(a));
                tagged GetBase                :