diff --git a/wolfcrypt/src/sha256.c b/wolfcrypt/src/sha256.c
index cad6f8028..059f224a7 100644
--- a/wolfcrypt/src/sha256.c
+++ b/wolfcrypt/src/sha256.c
@@ -25,6 +25,24 @@
 
 #include <wolfssl/wolfcrypt/settings.h>
 
+/*
+ * SHA256 Build Options:
+ * USE_SLOW_SHA256:            Reduces code size by not partially unrolling
+                                (~2KB smaller and ~25% slower) (default OFF)
+ * WOLFSSL_SHA256_BY_SPEC:     Uses the Ch/Maj based on SHA256 specification
+                                (default ON)
+ * WOLFSSL_SHA256_ALT_CH_MAJ:  Alternate Ch/Maj that is easier for compilers to
+                                optimize and recognize as SHA256 (default OFF)
+ * SHA256_MANY_REGISTERS:      A SHA256 version that keeps all data in registers
+                                and partial unrolled (default OFF)
+ */
+
+/* Default SHA256 to use Ch/Maj based on specification */
+#if !defined(WOLFSSL_SHA256_BY_SPEC) && !defined(WOLFSSL_SHA256_ALT_CH_MAJ)
+    #define WOLFSSL_SHA256_BY_SPEC
+#endif
+
+
 #if !defined(NO_SHA256) && !defined(WOLFSSL_ARMASM)
 
 #if defined(HAVE_FIPS) && \
@@ -582,10 +600,14 @@ static int InitSha256(wc_Sha256* sha256)
         0x90BEFFFAL, 0xA4506CEBL, 0xBEF9A3F7L, 0xC67178F2L
     };
 
+/* Both versions of Ch and Maj are logically the same, but with the second set
+    the compilers can recognize them better for optimization */
 #ifdef WOLFSSL_SHA256_BY_SPEC
+    /* SHA256 math based on specification */
     #define Ch(x,y,z)       ((z) ^ ((x) & ((y) ^ (z))))
     #define Maj(x,y,z)      ((((x) | (y)) & (z)) | ((x) & (y)))
 #else
+    /* SHA256 math reworked for easier compiler optimization */
     #define Ch(x,y,z)       ((((y) ^ (z)) & (x)) ^ (z))
     #define Maj(x,y,z)      ((((x) ^ (y)) & ((y) ^ (z))) ^ (y))
 #endif
@@ -679,6 +701,7 @@ static int InitSha256(wc_Sha256* sha256)
         return 0;
     }
 #else
+    /* SHA256 version that keeps all data in registers */
     #define SCHED1(j) (W[j] = sha256->buffer[j])
     #define SCHED(j) (               \
                    W[ j     & 15] += \
@@ -707,7 +730,7 @@ static int InitSha256(wc_Sha256* sha256)
     {
         word32 S[8], t0, t1;
         int i;
-        word32 W[16];
+        word32 W[WC_SHA256_BLOCK_SIZE/sizeof(word32)];
 
         /* Copy digest to working vars */
         S[0] = sha256->digest[0];
@@ -744,7 +767,7 @@ static int InitSha256(wc_Sha256* sha256)
 
         return 0;
     }
-#endif
+#endif /* SHA256_MANY_REGISTERS */
 #endif
 /* End wc_ software implementation */