diff --git a/Q6-cache/info.txt b/Q6-cache/info.txt
index b3d861e..3b0d10e 100644
--- a/Q6-cache/info.txt
+++ b/Q6-cache/info.txt
@@ -12,6 +12,6 @@
 
 Βήμα 1: Λόγος διάμεσων χρόνων: 20.265193309
 
-Βήμα 2: Λόγος διάμεσων χρόνων: xxxx
+Βήμα 2: Λόγος διάμεσων χρόνων: 24.61113257 (s=1024)
 
 Βήμα 3: Λόγος διάμεσων χρόνων: xxxx
\ No newline at end of file
diff --git a/Q6-cache/src/main.c b/Q6-cache/src/main.c
index 47d6093..09460ff 100644
--- a/Q6-cache/src/main.c
+++ b/Q6-cache/src/main.c
@@ -52,7 +52,16 @@ mMult_ft multSelect (char* order) {
    else                                            return matrixMult_ijk;
 }
 
+mMultBlock_ft multBlockSelect (char* order) {
+   if (! strcmp ((const char*)order, "ijk"))       return matrixMult_ijk_block;
+   else if (! strcmp ((const char*)order, "ikj"))  return matrixMult_ikj_block;
+   else if (! strcmp ((const char*)order, "jik"))  return matrixMult_jik_block;
+   else if (! strcmp ((const char*)order, "jki"))  return matrixMult_jki_block;
+   else if (! strcmp ((const char*)order, "kij"))  return matrixMult_kij_block;
+   else if (! strcmp ((const char*)order, "kji"))  return matrixMult_kji_block;
+   else                                            return matrixMult_ijk_block;
 
+}
 
 /*!
  * A unit testing like main function to profile our code
@@ -61,36 +70,48 @@ int main(int argc, char **argv) {
   struct timeval start, end;     /* time structs */
   double time[MAX_ITER] = {0.0}; /* execution time array in ms */
   float *A, *B, *C;              /* matrix declarations */
+  mMult_ft mMult =NULL;
+  mMultBlock_ft  mMultBlock =NULL;
 
   /* read matrix size (or use default) */
-  if (argc != 3){
+  if (argc < 3){
     fprintf( stderr,
           "Usage:\n"
-          "%s n order, where \n"
+          "%s n order [block], where \n"
           "   n: is the matrix size.\n"
-          "   order: the loop order ex: ijk , jik, ...\n",
+          "   order: the loop order ex: ijk , jik, ...\n"
+          "   block: Optional block size\n",
              argv[0]);
     exit(1);
   }
   int n = atoi( argv[1] );
-  mMult_ft  mMult =  multSelect(argv[2]);
+  if (argc == 4)
+      mMultBlock =  multBlockSelect(argv[2]);
+  else
+     mMult =  multSelect(argv[2]);
 
   /* initialize matrices */
   A = matrixInit( n );
   B = matrixInit( n );
   C = (float *) malloc( n*n*sizeof(float) );
 
-  /* compute matrix multiplication */
-  for (int it = 0; it < MAX_ITER; it++) {
-    gettimeofday(&start, NULL);
-    mMult( C, A, B, n );
-    gettimeofday(&end, NULL);
-
-    time[it] =  (end.tv_sec  - start.tv_sec)  * 1000.0 +    /* sec to ms */
-                (end.tv_usec - start.tv_usec) / 1000.0;     /* us to ms */
+   /* compute matrix multiplication */
+   for (int it = 0; it < MAX_ITER; it++) {
+      if (argc == 4) {
+         gettimeofday(&start, NULL);
+         mMultBlock( C, A, B, n, atoi(argv[3]) );
+         gettimeofday(&end, NULL);
+      }
+      else {
+         gettimeofday(&start, NULL);
+         mMult( C, A, B, n );
+         gettimeofday(&end, NULL);
+      }
+      time[it] =  (end.tv_sec  - start.tv_sec)  * 1000.0 +    /* sec to ms */
+                  (end.tv_usec - start.tv_usec) / 1000.0;     /* us to ms */
 
-    printf("Iter: %d Time: %f ms\n", it, time[it]);
-  }
+      printf("Iter: %d Time: %f ms\n", it, time[it]);
+   }
 
   /* we need to use the result -- verify it */
   for (int i = 0; i < n; i++) {             /* rows */
diff --git a/Q6-cache/src/matmul.c b/Q6-cache/src/matmul.c
index bf24135..0f495e0 100644
--- a/Q6-cache/src/matmul.c
+++ b/Q6-cache/src/matmul.c
@@ -116,7 +116,6 @@ void matrixMult_kij(float * const C, float const * const A, float const * const
  * \param   B  pointer to input matrix B
  * \param   n  Size of matrices (both sizes)
  * \return     none
- * xxx
  */
 void matrixMult_kji(float * const C, float const * const A, float const * const B, int const n) {
    for (int k = 0; k < n; ++k) {
@@ -132,6 +131,147 @@ void matrixMult_kji(float * const C, float const * const A, float const * const
    }
 }
 
+/*!
+ * Square Matrix multiplication in blocks - ijk
+ * \param   C  pointer to output matrix
+ * \param   A  pointer to input matrix A
+ * \param   B  pointer to input matrix B
+ * \param   n  Size of matrices (both sizes)
+ * \param   s  The block size
+ * \return     none
+ */
+void matrixMult_ijk_block(float * const C, float const * const A, float const * const B, int const n, int const s) {
+   for (int I =0; I<n; I +=s)
+      for (int J =0; J<n; J +=s)
+         for (int K = 0; K<n; K +=s)
+            for (int i =0; i<s; ++i)
+               for (int j =0; j<s; ++j) {
+                  int k =0;
+                  if (K+k == 0)
+                     C[ sub2ind(I+i,J+j,n) ] = 0;
+                  for (k =0; k<s; ++k)
+                     C[ sub2ind(I+i,J+j,n) ] += A[ sub2ind(I+i,K+k,n) ] * B[ sub2ind(K+k,J+j,n) ];
+               }
+}
+
+/*!
+ * Square Matrix multiplication in blocks - ikj
+ * \param   C  pointer to output matrix
+ * \param   A  pointer to input matrix A
+ * \param   B  pointer to input matrix B
+ * \param   n  Size of matrices (both sizes)
+ * \param   s  The block size
+ * \return     none
+ */
+void matrixMult_ikj_block(float * const C, float const * const A, float const * const B, int const n, int const s) {
+   for (int I =0; I<n; I +=s)
+      for (int K =0; K<n; K +=s)
+         for (int J = 0; J<n; J +=s)
+            for (int i =0; i<s; ++i)
+               for (int k =0; k<s; ++k) {
+                  if ((k+K) == 0) {
+                     for (int j =0; j<s; ++j)
+                        C[ sub2ind(I+i,J+j,n) ] = A[ sub2ind(I+i,K+k,n) ] * B[ sub2ind(K+k,J+j,n) ];
+                  }
+                  else {
+                     for (int j =0; j<s; ++j)
+                        C[ sub2ind(I+i,J+j,n) ] += A[ sub2ind(I+i,K+k,n) ] * B[ sub2ind(K+k,J+j,n) ];
+                  }
+               }
+}
+
+/*!
+ * Square Matrix multiplication in blocks - jik
+ * \param   C  pointer to output matrix
+ * \param   A  pointer to input matrix A
+ * \param   B  pointer to input matrix B
+ * \param   n  Size of matrices (both sizes)
+ * \param   s  The block size
+ * \return     none
+ */
+void matrixMult_jik_block(float * const C, float const * const A, float const * const B, int const n, int const s) {
+   for (int J =0; J<n; J +=s)
+      for (int I =0; I<n; I +=s)
+         for (int K = 0; K<n; K +=s)
+            for (int j =0; j<s; ++j)
+               for (int i =0; i<s; ++i) {
+                  int k =0;
+                  if (K+k == 0)
+                     C[ sub2ind(I+i,J+j,n) ] = 0;
+                  for (k =0; k<s; ++k)
+                     C[ sub2ind(I+i,J+j,n) ] += A[ sub2ind(I+i,K+k,n) ] * B[ sub2ind(K+k,J+j,n) ];
+               }
+}
+
+/*!
+ * Square Matrix multiplication in blocks - jki
+ * \param   C  pointer to output matrix
+ * \param   A  pointer to input matrix A
+ * \param   B  pointer to input matrix B
+ * \param   n  Size of matrices (both sizes)
+ * \param   s  The block size
+ * \return     none
+ */
+void matrixMult_jki_block(float * const C, float const * const A, float const * const B, int const n, int const s) {
+   for (int J =0; J<n; J +=s)
+      for (int K =0; K<n; K +=s)
+         for (int I = 0; I<n; I +=s)
+            for (int j =0; j<s; ++j)
+               for (int k =0; k<s; ++k) {
+                  if ((k+K) == 0) {
+                     for (int i =0; i<s; ++i)
+                        C[ sub2ind(I+i,J+j,n) ] = A[ sub2ind(I+i,K+k,n) ] * B[ sub2ind(K+k,J+j,n) ];
+                  }
+                  else {
+                     for (int i =0; i<s; ++i)
+                        C[ sub2ind(I+i,J+j,n) ] += A[ sub2ind(I+i,K+k,n) ] * B[ sub2ind(K+k,J+j,n) ];
+                  }
+               }
+}
+
+/*!
+ * Square Matrix multiplication in blocks - kij
+ * \param   C  pointer to output matrix
+ * \param   A  pointer to input matrix A
+ * \param   B  pointer to input matrix B
+ * \param   n  Size of matrices (both sizes)
+ * \param   s  The block size
+ * \return     none
+ *
+ * \warning
+ *    Calling this function will trigger undefined result. There is no initialization of C.
+ */
+void matrixMult_kij_block(float * const C, float const * const A, float const * const B, int const n, int const s) {
+   for (int K =0; K<n; K +=s)
+      for (int I =0; I<n; I +=s)
+         for (int J = 0; J<n; J +=s)
+            for (int k =0; k<s; ++k)
+               for (int i =0; i<s; ++i)
+                  for (int j =0; j<s; ++j)
+                     C[ sub2ind(I+i,J+j,n) ] += A[ sub2ind(I+i,K+k,n) ] * B[ sub2ind(K+k,J+j,n) ];
+}
+
+/*!
+ * Square Matrix multiplication in blocks - kji
+ * \param   C  pointer to output matrix
+ * \param   A  pointer to input matrix A
+ * \param   B  pointer to input matrix B
+ * \param   n  Size of matrices (both sizes)
+ * \param   s  The block size
+ * \return     none
+ *
+ * \warning
+ *    Calling this function will trigger undefined result. There is no initialization of C.
+ */
+void matrixMult_kji_block(float * const C, float const * const A, float const * const B, int const n, int const s) {
+   for (int K =0; K<n; K +=s)
+      for (int J =0; J<n; J +=s)
+         for (int I = 0; I<n; I +=s)
+            for (int k =0; k<s; ++k)
+               for (int j =0; j<s; ++j)
+                  for (int i =0; i<s; ++i)
+                     C[ sub2ind(I+i,J+j,n) ] += A[ sub2ind(I+i,K+k,n) ] * B[ sub2ind(K+k,J+j,n) ];
+}
 
 /*!
  * Initialize matrix with random indices and return the matrix pointer.
diff --git a/Q6-cache/src/matmul.h b/Q6-cache/src/matmul.h
index b148737..877cb74 100644
--- a/Q6-cache/src/matmul.h
+++ b/Q6-cache/src/matmul.h
@@ -16,7 +16,8 @@
 #define sub2ind(i,j,n) (j) + (i)*(n)
 
 //! Function pointer type to matrix multiplication back-end.
-typedef void (*mMult_ft)(float * const C, float const * const A, float const * const B, int const n);
+typedef void (*mMult_ft)(float * const, float const * const, float const * const, int const);
+typedef void (*mMultBlock_ft)(float * const, float const * const, float const * const, int const, int const);
 
 void matrixMult_ijk(float * const C, float const * const A, float const * const B, int const n);
 void matrixMult_ikj(float * const C, float const * const A, float const * const B, int const n);
@@ -25,6 +26,14 @@ void matrixMult_jki(float * const C, float const * const A, float const * const
 void matrixMult_kij(float * const C, float const * const A, float const * const B, int const n);
 void matrixMult_kji(float * const C, float const * const A, float const * const B, int const n);
 
+void matrixMult_ijk_block(float * const C, float const * const A, float const * const B, int const n, int const s);
+void matrixMult_ikj_block(float * const C, float const * const A, float const * const B, int const n, int const s);
+void matrixMult_jik_block(float * const C, float const * const A, float const * const B, int const n, int const s);
+void matrixMult_jki_block(float * const C, float const * const A, float const * const B, int const n, int const s);
+void matrixMult_kij_block(float * const C, float const * const A, float const * const B, int const n, int const s);
+void matrixMult_kji_block(float * const C, float const * const A, float const * const B, int const n, int const s);
+
+
 float* matrixInit(int const n);
 
 #endif /* SRC_MATMUL_H_ */