diff --git a/ggml/src/ggml-cpu/ggml-cpu.c b/ggml/src/ggml-cpu/ggml-cpu.c
index f63c87b03ca0..7debad319e74 100644
--- a/ggml/src/ggml-cpu/ggml-cpu.c
+++ b/ggml/src/ggml-cpu/ggml-cpu.c
@@ -1362,7 +1362,6 @@ UseGgmlGemm1:;
     if (src1->type != vec_dot_type) {
         char * wdata = params->wdata;
 
-        const size_t nbw0 = ggml_type_size(vec_dot_type);
         const size_t nbw1 = ggml_row_size(vec_dot_type, ne10);
         const size_t nbw2 = nbw1*ne11;
         const size_t nbw3 = nbw2*ne12;
@@ -1372,36 +1371,22 @@ UseGgmlGemm1:;
         GGML_ASSERT(src1->type == GGML_TYPE_F32 ||
                     (src1->type == GGML_TYPE_F16 && vec_dot_type == GGML_TYPE_F32));
 
-    #if 0
-        for (int64_t i13 = 0; i13 < ne13; ++i13) {
-            for (int64_t i12 = 0; i12 < ne12; ++i12) {
-                for (int64_t i11 = ith; i11 < ne11; i11 += nth) {
-                    from_float((float *)((char *) src1->data + i13*nb13 + i12*nb12 + i11*nb11),
-                               (void *)               (wdata + i13*nbw3 + i12*nbw2 + i11*nbw1),
-                                ne10);
-                }
-            }
-        }
-    #else
-        for (int64_t i13 = 0; i13 < ne13; ++i13) {
-            for (int64_t i12 = 0; i12 < ne12; ++i12) {
-                for (int64_t i11 = 0; i11 < ne11; ++i11) {
-                    size_t bs = ggml_blck_size(vec_dot_type);
-                    int64_t ne10_block_start = (ith * ne10/bs) / nth;
-                    int64_t ne10_block_end   = ((ith + 1) * ne10/bs) / nth;
-                    const char * src1_block = (const char *) src1->data + i13*nb13 + i12*nb12 + i11*nb11 + ne10_block_start*bs*nb10;
-                    char * dst_block = wdata + i13*nbw3 + i12*nbw2 + i11*nbw1 + ne10_block_start*nbw0;
-                    const int64_t n_block = (ne10_block_end - ne10_block_start) * bs;
-
-                    if (src1->type == GGML_TYPE_F32) {
-                        from_float((const float *) src1_block, dst_block, n_block);
-                    } else {
-                        ggml_cpu_fp16_to_fp32((const ggml_fp16_t *) src1_block, (float *) dst_block, n_block);
-                    }
-                }
+        // one thread per src1 row: splitting a row across threads makes several cores write the same
+        // cache lines, and every later vec_dot read of the row gets slow (10x on a 2-socket Xeon)
+        const int64_t nr1 = ne11*ne12*ne13;
+        for (int64_t ir = ith; ir < nr1; ir += nth) {
+            const int64_t i13 = ir/(ne12*ne11);
+            const int64_t i12 = (ir - i13*ne12*ne11)/ne11;
+            const int64_t i11 = ir - i13*ne12*ne11 - i12*ne11;
+            const char * src1_row = (const char *) src1->data + i13*nb13 + i12*nb12 + i11*nb11;
+            char * dst_row = wdata + i13*nbw3 + i12*nbw2 + i11*nbw1;
+
+            if (src1->type == GGML_TYPE_F32) {
+                from_float((const float *) src1_row, dst_row, ne10);
+            } else {
+                ggml_cpu_fp16_to_fp32((const ggml_fp16_t *) src1_row, (float *) dst_row, ne10);
             }
         }
-    #endif
     }
 
     if (ith == 0) {