diff --git a/star/cpiohdr.c b/star/cpiohdr.c
index 9c7a774..2785661 100644
--- a/star/cpiohdr.c
+++ b/star/cpiohdr.c
@@ -536,7 +536,9 @@ cpio_checkswab(ptb)
 }
 
 /*
- * This simple sum is used for the SYSvr4 file content CRC
+ * This simple sum is used for the SYSvr4 file content checksum.  This is
+ * implemented like Sum32 algorithm.
+ *
  * Use Int32_t to implement the same behavior as the AT&T cpio command.
  */
 LOCAL Int32_t
diff --git a/star/star.1 b/star/star.1
index 95b202c..a931a6f 100644
--- a/star/star.1
+++ b/star/star.1
@@ -913,9 +913,9 @@ archive format because of its limited portability.
 .B crc
 This format is similar to the
 .B asc
-cpio format but in addition uses a simple byte based checksum called
+cpio format but in addition uses a simple byte based checksum called here as
 .BR CRC .
-Try to avoid the
+This algorithm is simple Sum32 -- not a polynomial CRC.  Try to avoid the
 .B crc
 archive format because of its limited portability.