diff --git a/src/basic/math_trans/poly_log.s b/src/basic/math_trans/b9c1.poly_log.s
similarity index 63%
rename from src/basic/math_trans/poly_log.s
rename to src/basic/math_trans/b9c1.poly_log.s
index 3f770ac9..139d4c83 100644
--- a/src/basic/math_trans/poly_log.s
+++ b/src/basic/math_trans/b9c1.poly_log.s
@@ -3,8 +3,13 @@
 ;; #LAYOUT# *  BASIC_0  #TAKE
 ;; #LAYOUT# *   *       #IGNORE
 
+
+; This file is under the MIT license, it contains code released by Microsoft Corporation.
+; See LICENSE for more information.
+
 ; Polynomial for the logarithm function
 
+; This is verified to be identical to the original Microsoft implementation where it was named LOGCN2
 
 !ifdef CONFIG_TRANSCENDENTAL_FUNCTIONS {
 
diff --git a/tools/similarity.c b/tools/similarity.c
index 27ce8909..8fabb438 100644
--- a/tools/similarity.c
+++ b/tools/similarity.c
@@ -20,13 +20,14 @@ int matches[MAX_SIZE];
 
 int phase_mask[MAX_SIZE+MAX_SIZE];
 
-#define NUM_CHUNKS 9
+#define NUM_CHUNKS 10
 // Pairs of start, end memory addresses of known exact similarity with the open source Microsoft BASIC
 unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
     0xB391, 0xB39D,
     0xB3A2, 0xB3A5,
     0xB849, 0xB97D,
     0xB983, 0xB9BB,
+    0xB9C1, 0xB9D5,
     0xBA28, 0xBCF2,
     0xBD7E, 0xBD90,
     0xBDB3, 0xBDC1,