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diff --git a/openpower/sv/bitmanip/appendix.mdwn b/openpower/sv/bitmanip/appendix.mdwn
index 9f25e0dbea99120cc7655cd3ca3b999c65f25ed8..ffd7bda508323d6f5dc6a6bccbf5f431801a66a2 100644 (file)
--- a/openpower/sv/bitmanip/appendix.mdwn
+++ b/openpower/sv/bitmanip/appendix.mdwn
@@ -188,7 +188,10 @@ As a result, a big-integer subtract and multiply may be carried out
 in only 3 instructions, one of which is setting a scalar integer to
 zero.
 
-## EXT004 Opcode map
+An Rc=1 variant tests not against RT but RA, which allows detection
+of a fixup in Knuth Algorithm D: the condition where RA is not zero.
+
+# EXT004 Opcode map
 
 See Power ISA v3.1, Book III, Appendix D, Table 13 (sheet 7 of 8), p1357.
 Proposed is the addition of `msubxd` (**DRAFT, NOT APPROVED**) which is