x11: switch to intensity 20 for SM>=5.2 750+970

x11/x11.cu

@@ -136,7 +136,8 @@ extern "C" int scanhash_x11(int thr_id, uint32_t *pdata,
 {
 	const uint32_t first_nonce = pdata[19];
 	static bool init[8] = {0,0,0,0,0,0,0,0};
-	int throughput = opt_work_size ? opt_work_size : (1 << 19); // 256*256*8;
+	int intensity = (device_sm[device_map[thr_id]] >= 500) ? 20 : 19;
+	int throughput = opt_work_size ? opt_work_size : (1 << intensity); // 20=256*256*16;
 	throughput = min(throughput, max_nonce - first_nonce);
 
 	if (opt_benchmark)