diff --git a/ci/blackbox.sh b/ci/blackbox.sh
index c44dc238..5ba7a29a 100755
--- a/ci/blackbox.sh
+++ b/ci/blackbox.sh
@@ -12,7 +12,7 @@ VORTEX_HOME=$SCRIPT_DIR/..
 DRIVER=vlsim
 APP=sgemm
 CLUSTERS=1
-CORES=2
+CORES=1
 WARPS=4
 THREADS=4
 L2=0
diff --git a/hw/rtl/VX_decode.sv b/hw/rtl/VX_decode.sv
index c2a6cac8..7186a553 100644
--- a/hw/rtl/VX_decode.sv
+++ b/hw/rtl/VX_decode.sv
@@ -380,7 +380,8 @@ module VX_decode  #(
                     3'h5: begin
                         op_type = `INST_OP_BITS'(`INST_GPU_TEX);
                         op_mod  = `INST_MOD_BITS'(func2);
-                        use_rd  = 1;                     
+                        use_rd  = 1;       
+                        `USED_IREG (rd);              
                         `USED_IREG (rs1);
                         `USED_IREG (rs2);
                         `USED_IREG (rs3);
diff --git a/hw/rtl/VX_warp_sched.sv b/hw/rtl/VX_warp_sched.sv
index 9495c001..979a3536 100644
--- a/hw/rtl/VX_warp_sched.sv
+++ b/hw/rtl/VX_warp_sched.sv
@@ -71,8 +71,8 @@ module VX_warp_sched #(
 
             // activate first warp
             warp_pcs[0]     <= `STARTUP_ADDR;
-            active_warps[0] <= '1;
-            thread_masks[0] <= '1;
+            active_warps[0] <= 1;
+            thread_masks[0] <= 1;
         end else begin            
             if (warp_ctl_if.valid && warp_ctl_if.wspawn.valid) begin
                 use_wspawn <= warp_ctl_if.wspawn.wmask & (~`NUM_WARPS'(1));