diff --git a/samples/99_matrixexperiments/main.cpp b/samples/99_matrixexperiments/main.cpp
index fae01b3..a002514 100644
--- a/samples/99_matrixexperiments/main.cpp
+++ b/samples/99_matrixexperiments/main.cpp
@@ -881,12 +881,12 @@ int main(int argc, char** argv)
     }
 
     if (mask & 0x400) {
-        bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 1, 1>(context, program, queue, C, A, B, M, N, K, C_ref);
-        bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 2, 1>(context, program, queue, C, A, B, M, N, K, C_ref);
-        bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 1, 2>(context, program, queue, C, A, B, M, N, K, C_ref);
-        bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 2, 2>(context, program, queue, C, A, B, M, N, K, C_ref);
-        bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 4, 2>(context, program, queue, C, A, B, M, N, K, C_ref);
-        bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 2, 4>(context, program, queue, C, A, B, M, N, K, C_ref);
+        //bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 1, 1>(context, program, queue, C, A, B, M, N, K, C_ref);
+        //bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 2, 1>(context, program, queue, C, A, B, M, N, K, C_ref);
+        //bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 1, 2>(context, program, queue, C, A, B, M, N, K, C_ref);
+        //bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 2, 2>(context, program, queue, C, A, B, M, N, K, C_ref);
+        //bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 4, 2>(context, program, queue, C, A, B, M, N, K, C_ref);
+        //bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 2, 4>(context, program, queue, C, A, B, M, N, K, C_ref);
         bfloat16_dpas_blockread_rowmajor_tiled<8, 16, 4, 4>(context, program, queue, C, A, B, M, N, K, C_ref);
     }
 
diff --git a/samples/99_matrixexperiments/matrix_kernel_tiled.cl b/samples/99_matrixexperiments/matrix_kernel_tiled.cl
index 39d23ad..a8d6b4d 100644
--- a/samples/99_matrixexperiments/matrix_kernel_tiled.cl
+++ b/samples/99_matrixexperiments/matrix_kernel_tiled.cl
@@ -465,6 +465,9 @@ void HELPER_NAME(btile_block_load_rowmajor, MM, NN)(global ushort* B, int tN, in
     if (KK % 2 == 0 & NN % 2 == 0) {
         for (int kk = 0; kk < KK; kk+=2) {
             for (int nn = 0; nn < NN; nn+=2) {
+                //if (get_sub_group_local_id() == 0) {
+                //    printf("btile block load: %d, %d, %2d: n = %3d, k = %3d, nn = %2d, kk = %2d, coord = %3d, %3d\n", (int)get_group_id(1), (int)get_group_id(0), get_sub_group_id(), n, k, nn, kk, n + nn * tN, k + kk * tK);
+                //}
                 int8 tmp[2][2];
                 intel_subgroup_block_read_transform_u16_k32n16v2(B, N * sizeof(ushort), K, N * sizeof(ushort), (int2)(n + nn * tN, k + kk * tK), tmp);
                 for (int tnn = 0; tnn < 2; tnn++) {
@@ -555,11 +558,14 @@ void HELPER_NAME(atile_block_prefetch_rowmajor, MM, NN)(global ushort* A, int tM
 
 void HELPER_NAME(btile_block_prefetch_rowmajor, MM, NN)(global ushort* B, int tN, int K, int N, int k, int n)
 {
-    if (KK % 2 == 0 & NN == 4 & SGS_PER_WG_Y >= 2) {
-        const int nn = (get_sub_group_id() / SGS_PER_WG_X) % 2 * 2;
-        for (int kk = 0; kk < KK; kk+=2) {
-            intel_subgroup_block_prefetch_u16_m32k16v2(B, N * sizeof(ushort), K, N * sizeof(ushort), (int2)(n + nn * tN, k + kk * tK));
-        }
+    if (KK == 2 & NN == 4 & SGS_PER_WG_Y >= 4) {
+        const int sg_index_y = get_sub_group_id() / SGS_PER_WG_X;   // index in [0, SGS_PER_WG_Y)
+        const int nn = sg_index_y % 2 * 2;  // nn(sg_index_y) == 0, 2, 0, 2, 0, 2, 0, 2, ...
+        const int kk = sg_index_y / 2 % 2;  // kk(sg_index_y) == 0, 0, 1, 1, 0, 0, 1, 1, ...
+        //if (get_sub_group_local_id() == 0) {
+        //    printf("btile block prefetch: %d, %d, %2d: sg_y = %d, n = %3d, k = %3d, nn = %2d, kk = %2d, coord = %3d, %3d\n", (int)get_group_id(1), (int)get_group_id(0), get_sub_group_id(), sg_index_y, n, k, nn, kk, n + nn * tN, k + kk * tK);
+        //}
+        intel_subgroup_block_prefetch_u16_m16k16v2(B, N * sizeof(ushort), K, N * sizeof(ushort), (int2)(n + nn * tN, k + kk * tK));
     } else if (KK % 2 == 0 & NN % 2 == 0) {
         for (int kk = 0; kk < KK; kk+=2) {
             for (int nn = 0; nn < NN; nn += 2) {
@@ -589,11 +595,11 @@ void HELPER_NAME(btile_block_prefetch_rowmajor, MM, NN)(global ushort* B, int tN
 
 void HELPER_NAME(btile_block_prefetch_vnni, MM, NN)(global ushort* B, int tN, int K, int N, int k, int n)
 {
-    if (KK % 2 == 0 & NN == 4 & SGS_PER_WG_Y >= 4) {
-        const int nn = (get_sub_group_id() / SGS_PER_WG_X) % 4;
-        for (int kk = 0; kk < KK; kk+=2) {
-            intel_subgroup_block_prefetch_u32_m16k16(B, N * sizeof(uint), K, N * sizeof(uint), (int2)(n + nn * tN, (k + kk * tK) / 2));
-        }
+    if (KK == 2 & NN == 4 & SGS_PER_WG_Y >= 4) {
+        const int sg_index_y = get_sub_group_id() / SGS_PER_WG_X;   // index in [0, SGS_PER_WG_Y)
+        const int nn = sg_index_y % 4;  // nn(sg_index_y) == 0, 1, 2, 3, 0, 1, 2, 3
+        const int kk = 0;               // kk(sg_index_y) == 0, 0, 0, 0, 0, 0, 0, 0
+        intel_subgroup_block_prefetch_u32_m16k16(B, N * sizeof(uint), K, N * sizeof(uint), (int2)(n + nn * tN, (k + kk * tK) / 2));
     } else if (KK % 2 == 0) {
         for (int kk = 0; kk < KK; kk+=2) {
             for (int nn = 0; nn < NN; nn++) {