diff --git a/openfpga_flow/vpr_arch/README.md b/openfpga_flow/vpr_arch/README.md
index e5855b390..c0286df54 100644
--- a/openfpga_flow/vpr_arch/README.md
+++ b/openfpga_flow/vpr_arch/README.md
@@ -21,6 +21,7 @@ Please reveal the following architecture features in the names to help quickly s
 - multi\_io\_capacity: If I/O capacity is different on each side of FPGAs.
 - reduced\_io: If I/Os only appear a certain or multiple sides of FPGAs 
 - registerable\_io: If I/Os are registerable (can be either combinational or sequential)
+- CustomIoLoc: Use OpenFPGA's extended custom I/O location syntax
 - <feature\_size>: The technology node which the delay numbers are extracted from.
 - TileOrgz<Type>: How tile is organized. 
   * Top-left (Tl): the pins of a tile are placed on the top side and left side only
diff --git a/openfpga_flow/vpr_arch/k4_N4_tileable_customIoLoc_40nm.xml b/openfpga_flow/vpr_arch/k4_N4_tileable_customIoLoc_40nm.xml
new file mode 100644
index 000000000..ebdc7bfa1
--- /dev/null
+++ b/openfpga_flow/vpr_arch/k4_N4_tileable_customIoLoc_40nm.xml
@@ -0,0 +1,369 @@
+<!-- 
+  Architecture with no fracturable LUTs
+
+  - 40 nm technology
+  - General purpose logic block: 
+    K = 4, N = 4
+  - Routing architecture: L = 4, fc_in = 0.15, Fc_out = 0.1
+
+  Details on Modelling:
+
+  Based on flagship k6_frac_N10_mem32K_40nm.xml architecture.  This architecture has no fracturable LUTs nor any heterogeneous blocks.
+
+
+  Authors: Jason Luu, Jeff Goeders, Vaughn Betz
+-->
+<architecture>
+  <!-- 
+       ODIN II specific config begins 
+       Describes the types of user-specified netlist blocks (in blif, this corresponds to 
+       ".model [type_of_block]") that this architecture supports.
+
+       Note: Basic LUTs, I/Os, and flip-flops are not included here as there are 
+       already special structures in blif (.names, .input, .output, and .latch) 
+       that describe them.
+  -->
+  <models>
+    <!-- A virtual model for I/O to be used in the physical mode of io block -->
+    <model name="io">
+      <input_ports>
+        <port name="outpad"/>
+      </input_ports>
+      <output_ports>
+        <port name="inpad"/>
+      </output_ports>
+    </model>
+  </models>
+  <tiles>
+    <tile name="io_top" capacity="8" area="0">
+      <equivalent_sites>
+        <site pb_type="io"/>
+      </equivalent_sites>
+      <input name="outpad" num_pins="1"/>
+      <output name="inpad" num_pins="1"/>
+      <fc in_type="frac" in_val="0.15" out_type="frac" out_val="0.10"/>
+      <pinlocations pattern="custom">
+        <loc side="bottom">io[0:3].inpad io[0:7].outpad io[4:7].inpad</loc>
+      </pinlocations>
+    </tile>
+    <tile name="io_bottom" capacity="6" area="0">
+      <equivalent_sites>
+        <site pb_type="io"/>
+      </equivalent_sites>
+      <input name="outpad" num_pins="1"/>
+      <output name="inpad" num_pins="1"/>
+      <fc in_type="frac" in_val="0.15" out_type="frac" out_val="0.10"/>
+      <pinlocations pattern="custom">
+        <loc side="top">io[0:4].outpad io[0:1].inpad io[5:7].outpad io[2:7].inpad</loc>
+      </pinlocations>
+    </tile>
+    <tile name="io_left" capacity="4" area="0">
+      <equivalent_sites>
+        <site pb_type="io"/>
+      </equivalent_sites>
+      <input name="outpad" num_pins="1"/>
+      <output name="inpad" num_pins="1"/>
+      <fc in_type="frac" in_val="0.15" out_type="frac" out_val="0.10"/>
+      <pinlocations pattern="custom">
+        <loc side="right">io.inpad io.outpad</loc>
+      </pinlocations>
+    </tile>
+    <tile name="io_right" capacity="2" area="0">
+      <equivalent_sites>
+        <site pb_type="io"/>
+      </equivalent_sites>
+      <input name="outpad" num_pins="1"/>
+      <output name="inpad" num_pins="1"/>
+      <fc in_type="frac" in_val="0.15" out_type="frac" out_val="0.10"/>
+      <pinlocations pattern="custom">
+        <loc side="left">io[3:0].inpad io[7:0].outpad io[4:7].inpad</loc>
+      </pinlocations>
+    </tile>
+    <tile name="clb" area="53894">
+      <equivalent_sites>
+        <site pb_type="clb"/>
+      </equivalent_sites>
+      <input name="I" num_pins="10" equivalent="full"/>
+      <output name="O" num_pins="4" equivalent="none"/>
+      <clock name="clk" num_pins="1"/>
+      <fc in_type="frac" in_val="0.15" out_type="frac" out_val="0.10"/>
+      <pinlocations pattern="spread"/>
+    </tile>
+  </tiles>
+  <!-- ODIN II specific config ends -->
+  <!-- Physical descriptions begin -->
+  <layout tileable="true">
+    <auto_layout aspect_ratio="1.0">
+      <!--Perimeter of 'io' blocks with 'EMPTY' blocks at corners-->
+      <row type="io_top" starty="H-1" priority="100"/>
+      <row type="io_bottom" starty="0" priority="100"/>
+      <col type="io_left" startx="0" priority="100"/>
+      <col type="io_right" startx="W-1" priority="100"/>
+      <corners type="EMPTY" priority="101"/>
+      <!--Fill with 'clb'-->
+      <fill type="clb" priority="10"/>
+    </auto_layout>
+    <fixed_layout name="2x2" width="4" height="4">
+      <!--Perimeter of 'io' blocks with 'EMPTY' blocks at corners-->
+      <row type="io_top" starty="H-1" priority="100"/>
+      <row type="io_bottom" starty="0" priority="100"/>
+      <col type="io_left" startx="0" priority="100"/>
+      <col type="io_right" startx="W-1" priority="100"/>
+      <corners type="EMPTY" priority="101"/>
+      <!--Fill with 'clb'-->
+      <fill type="clb" priority="10"/>
+    </fixed_layout>
+    <fixed_layout name="4x4" width="6" height="6">
+      <!--Perimeter of 'io' blocks with 'EMPTY' blocks at corners-->
+      <row type="io_top" starty="H-1" priority="100"/>
+      <row type="io_bottom" starty="0" priority="100"/>
+      <col type="io_left" startx="0" priority="100"/>
+      <col type="io_right" startx="W-1" priority="100"/>
+      <corners type="EMPTY" priority="101"/>
+      <!--Fill with 'clb'-->
+      <fill type="clb" priority="10"/>
+    </fixed_layout>
+    <fixed_layout name="48x48" width="50" height="50">
+      <!--Perimeter of 'io' blocks with 'EMPTY' blocks at corners-->
+      <row type="io_top" starty="H-1" priority="100"/>
+      <row type="io_bottom" starty="0" priority="100"/>
+      <col type="io_left" startx="0" priority="100"/>
+      <col type="io_right" startx="W-1" priority="100"/>
+      <corners type="EMPTY" priority="101"/>
+      <!--Fill with 'clb'-->
+      <fill type="clb" priority="10"/>
+    </fixed_layout>
+    <fixed_layout name="72x72" width="74" height="74">
+      <!--Perimeter of 'io' blocks with 'EMPTY' blocks at corners-->
+      <row type="io_top" starty="H-1" priority="100"/>
+      <row type="io_bottom" starty="0" priority="100"/>
+      <col type="io_left" startx="0" priority="100"/>
+      <col type="io_right" startx="W-1" priority="100"/>
+      <corners type="EMPTY" priority="101"/>
+      <!--Fill with 'clb'-->
+      <fill type="clb" priority="10"/>
+    </fixed_layout>
+    <fixed_layout name="96x96" width="98" height="98">
+      <!--Perimeter of 'io' blocks with 'EMPTY' blocks at corners-->
+      <row type="io_top" starty="H-1" priority="100"/>
+      <row type="io_bottom" starty="0" priority="100"/>
+      <col type="io_left" startx="0" priority="100"/>
+      <col type="io_right" startx="W-1" priority="100"/>
+      <corners type="EMPTY" priority="101"/>
+      <!--Fill with 'clb'-->
+      <fill type="clb" priority="10"/>
+    </fixed_layout>
+  </layout>
+  <device>
+    <!-- VB & JL: Using Ian Kuon's transistor sizing and drive strength data for routing, at 40 nm. Ian used BPTM 
+			     models. We are modifying the delay values however, to include metal C and R, which allows more architecture
+			     experimentation. We are also modifying the relative resistance of PMOS to be 1.8x that of NMOS
+			     (vs. Ian's 3x) as 1.8x lines up with Jeff G's data from a 45 nm process (and is more typical of 
+			     45 nm in general). I'm upping the Rmin_nmos from Ian's just over 6k to nearly 9k, and dropping 
+			     RminW_pmos from 18k to 16k to hit this 1.8x ratio, while keeping the delays of buffers approximately
+			     lined up with Stratix IV. 
+			     We are using Jeff G.'s capacitance data for 45 nm (in tech/ptm_45nm).
+			     Jeff's tables list C in for transistors with widths in multiples of the minimum feature size (45 nm).
+			     The minimum contactable transistor is 2.5 * 45 nm, so I need to multiply drive strength sizes in this file
+	                     by 2.5x when looking up in Jeff's tables.
+			     The delay values are lined up with Stratix IV, which has an architecture similar to this
+			     proposed FPGA, and which is also 40 nm 
+			     C_ipin_cblock: input capacitance of a track buffer, which VPR assumes is a single-stage
+			     4x minimum drive strength buffer. -->
+    <sizing R_minW_nmos="8926" R_minW_pmos="16067"/>
+    <!-- The grid_logic_tile_area below will be used for all blocks that do not explicitly set their own (non-routing)
+     	  area; set to 0 since we explicitly set the area of all blocks currently in this architecture file.
+	  -->
+    <area grid_logic_tile_area="0"/>
+    <chan_width_distr>
+      <x distr="uniform" peak="1.000000"/>
+      <y distr="uniform" peak="1.000000"/>
+    </chan_width_distr>
+    <switch_block type="wilton" fs="3"/>
+    <connection_block input_switch_name="ipin_cblock"/>
+  </device>
+  <switchlist>
+    <!-- VB: the mux_trans_size and buf_size data below is in minimum width transistor *areas*, assuming the purple
+	       book area formula. This means the mux transistors are about 5x minimum drive strength.
+	       We assume the first stage of the buffer is 3x min drive strength to be reasonable given the large 
+	       mux transistors, and this gives a reasonable stage ratio of a bit over 5x to the second stage. We assume
+	       the n and p transistors in the first stage are equal-sized to lower the buffer trip point, since it's fed
+	       by a pass transistor mux. We can then reverse engineer the buffer second stage to hit the specified 
+	       buf_size (really buffer area) - 16.2x minimum drive nmos and 1.8*16.2 = 29.2x minimum drive.
+	       I then took the data from Jeff G.'s PTM modeling of 45 nm to get the Cin (gate of first stage) and Cout 
+	       (diff of second stage) listed below.  Jeff's models are in tech/ptm_45nm, and are in min feature multiples.
+	       The minimum contactable transistor is 2.5 * 45 nm, so I need to multiply the drive strength sizes above by 
+	       2.5x when looking up in Jeff's tables.
+	       Finally, we choose a switch delay (58 ps) that leads to length 4 wires having a delay equal to that of SIV of 126 ps.
+	       This also leads to the switch being 46% of the total wire delay, which is reasonable. -->
+    <switch type="mux" name="0" R="551" Cin=".77e-15" Cout="4e-15" Tdel="58e-12" mux_trans_size="2.630740" buf_size="27.645901"/>
+    <!--switch ipin_cblock resistance set to yeild for 4x minimum drive strength buffer-->
+    <switch type="mux" name="ipin_cblock" R="2231.5" Cout="0." Cin="1.47e-15" Tdel="7.247000e-11" mux_trans_size="1.222260" buf_size="auto"/>
+  </switchlist>
+  <segmentlist>
+    <!--- VB & JL: using ITRS metal stack data, 96 nm half pitch wires, which are intermediate metal width/space.  
+			     With the 96 nm half pitch, such wires would take 60 um of height, vs. a 90 nm high (approximated as square) Stratix IV tile so this seems
+			     reasonable. Using a tile length of 90 nm, corresponding to the length of a Stratix IV tile if it were square. -->
+    <segment name="L4" freq="1.000000" length="4" type="unidir" Rmetal="101" Cmetal="22.5e-15">
+      <mux name="0"/>
+      <sb type="pattern">1 1 1 1 1</sb>
+      <cb type="pattern">1 1 1 1</cb>
+    </segment>
+  </segmentlist>
+  <complexblocklist>
+    <!-- Define I/O pads begin -->
+    <!-- Capacity is a unique property of I/Os, it is the maximum number of I/Os that can be placed at the same (X,Y) location on the FPGA -->
+    <!-- Not sure of the area of an I/O (varies widely), and it's not relevant to the design of the FPGA core, so we're setting it to 0. -->
+    <pb_type name="io">
+      <input name="outpad" num_pins="1"/>
+      <output name="inpad" num_pins="1"/>
+      <!-- A mode denotes the physical implementation of an I/O 
+           This mode will be not packable but is mainly used for fabric verilog generation   
+        -->
+      <mode name="physical" disable_packing="true">
+        <pb_type name="iopad" blif_model=".subckt io" num_pb="1">
+          <input name="outpad" num_pins="1"/>
+          <output name="inpad" num_pins="1"/>
+        </pb_type>
+        <interconnect>
+          <direct name="outpad" input="io.outpad" output="iopad.outpad">
+            <delay_constant max="1.394e-11" in_port="io.outpad" out_port="iopad.outpad"/>
+          </direct>
+          <direct name="inpad" input="iopad.inpad" output="io.inpad">
+            <delay_constant max="4.243e-11" in_port="iopad.inpad" out_port="io.inpad"/>
+          </direct>
+        </interconnect>
+      </mode>
+      <!-- IOs can operate as either inputs or outputs.
+	     Delays below come from Ian Kuon. They are small, so they should be interpreted as
+	     the delays to and from registers in the I/O (and generally I/Os are registered 
+	     today and that is when you timing analyze them.
+	     -->
+      <mode name="inpad">
+        <pb_type name="inpad" blif_model=".input" num_pb="1">
+          <output name="inpad" num_pins="1"/>
+        </pb_type>
+        <interconnect>
+          <direct name="inpad" input="inpad.inpad" output="io.inpad">
+            <delay_constant max="4.243e-11" in_port="inpad.inpad" out_port="io.inpad"/>
+          </direct>
+        </interconnect>
+      </mode>
+      <mode name="outpad">
+        <pb_type name="outpad" blif_model=".output" num_pb="1">
+          <input name="outpad" num_pins="1"/>
+        </pb_type>
+        <interconnect>
+          <direct name="outpad" input="io.outpad" output="outpad.outpad">
+            <delay_constant max="1.394e-11" in_port="io.outpad" out_port="outpad.outpad"/>
+          </direct>
+        </interconnect>
+      </mode>
+      <!-- Every input pin is driven by 15% of the tracks in a channel, every output pin is driven by 10% of the tracks in a channel -->
+      <!-- IOs go on the periphery of the FPGA, for consistency, 
+          make it physically equivalent on all sides so that only one definition of I/Os is needed.
+          If I do not make a physically equivalent definition, then I need to define 4 different I/Os, one for each side of the FPGA
+        -->
+      <!-- Place I/Os on the sides of the FPGA -->
+      <power method="ignore"/>
+    </pb_type>
+    <!-- Define I/O pads ends -->
+    <!-- Define general purpose logic block (CLB) begin -->
+    <!--- Area calculation: Total Stratix IV tile area is about 8100 um^2, and a minimum width transistor 
+	   area is 60 L^2 yields a tile area of 84375 MWTAs.
+	   Routing at W=300 is 30481 MWTAs, leaving us with a total of 53000 MWTAs for logic block area 
+	   This means that only 37% of our area is in the general routing, and 63% is inside the logic
+	   block. Note that the crossbar / local interconnect is considered part of the logic block
+	   area in this analysis. That is a lower proportion of of routing area than most academics
+	   assume, but note that the total routing area really includes the crossbar, which would push
+	   routing area up significantly, we estimate into the ~70% range. 
+	   -->
+    <pb_type name="clb">
+      <input name="I" num_pins="10" equivalent="full"/>
+      <output name="O" num_pins="4" equivalent="none"/>
+      <clock name="clk" num_pins="1"/>
+      <!-- Describe basic logic element.  
+             Each basic logic element has a 4-LUT that can be optionally registered
+        -->
+      <pb_type name="fle" num_pb="4">
+        <input name="in" num_pins="4"/>
+        <output name="out" num_pins="1"/>
+        <clock name="clk" num_pins="1"/>
+        <!-- 4-LUT mode definition begin -->
+        <mode name="n1_lut4">
+          <!-- Define 4-LUT mode -->
+          <pb_type name="ble4" num_pb="1">
+            <input name="in" num_pins="4"/>
+            <output name="out" num_pins="1"/>
+            <clock name="clk" num_pins="1"/>
+            <!-- Define LUT -->
+            <pb_type name="lut4" blif_model=".names" num_pb="1" class="lut">
+              <input name="in" num_pins="4" port_class="lut_in"/>
+              <output name="out" num_pins="1" port_class="lut_out"/>
+              <!-- LUT timing using delay matrix -->
+              <delay_matrix type="max" in_port="lut4.in" out_port="lut4.out">
+                261e-12
+                261e-12
+                261e-12
+                261e-12
+              </delay_matrix>
+            </pb_type>
+            <!-- Define flip-flop -->
+            <pb_type name="ff" blif_model=".latch" num_pb="1" class="flipflop">
+              <input name="D" num_pins="1" port_class="D"/>
+              <output name="Q" num_pins="1" port_class="Q"/>
+              <clock name="clk" num_pins="1" port_class="clock"/>
+              <T_setup value="66e-12" port="ff.D" clock="clk"/>
+              <T_clock_to_Q max="124e-12" port="ff.Q" clock="clk"/>
+            </pb_type>
+            <interconnect>
+              <direct name="direct1" input="ble4.in" output="lut4[0:0].in"/>
+              <direct name="direct2" input="lut4.out" output="ff.D">
+                <!-- Advanced user option that tells CAD tool to find LUT+FF pairs in netlist -->
+                <pack_pattern name="ble4" in_port="lut4.out" out_port="ff.D"/>
+              </direct>
+              <direct name="direct3" input="ble4.clk" output="ff.clk"/>
+              <mux name="mux1" input="ff.Q lut4.out" output="ble4.out">
+                <!-- LUT to output is faster than FF to output on a Stratix IV -->
+                <delay_constant max="25e-12" in_port="lut4.out" out_port="ble4.out"/>
+                <delay_constant max="45e-12" in_port="ff.Q" out_port="ble4.out"/>
+              </mux>
+            </interconnect>
+          </pb_type>
+          <interconnect>
+            <direct name="direct1" input="fle.in" output="ble4.in"/>
+            <direct name="direct2" input="ble4.out" output="fle.out[0:0]"/>
+            <direct name="direct3" input="fle.clk" output="ble4.clk"/>
+          </interconnect>
+        </mode>
+        <!-- 6-LUT mode definition end -->
+      </pb_type>
+      <interconnect>
+        <!-- We use a full crossbar to get logical equivalence at inputs of CLB 
+		     The delays below come from Stratix IV. the delay through a connection block
+		     input mux + the crossbar in Stratix IV is 167 ps. We already have a 72 ps 
+		     delay on the connection block input mux (modeled by Ian Kuon), so the remaining
+		     delay within the crossbar is 95 ps. 
+		     The delays of cluster feedbacks in Stratix IV is 100 ps, when driven by a LUT.
+		     Since all our outputs LUT outputs go to a BLE output, and have a delay of 
+		     25 ps to do so, we subtract 25 ps from the 100 ps delay of a feedback
+		     to get the part that should be marked on the crossbar.	 -->
+        <complete name="crossbar" input="clb.I fle[3:0].out" output="fle[3:0].in">
+          <delay_constant max="95e-12" in_port="clb.I" out_port="fle[3:0].in"/>
+          <delay_constant max="75e-12" in_port="fle[3:0].out" out_port="fle[3:0].in"/>
+        </complete>
+        <complete name="clks" input="clb.clk" output="fle[3:0].clk">
+        </complete>
+        <!-- This way of specifying direct connection to clb outputs is important because this architecture uses automatic spreading of opins.  
+               By grouping to output pins in this fashion, if a logic block is completely filled by 6-LUTs, 
+               then the outputs those 6-LUTs take get evenly distributed across all four sides of the CLB instead of clumped on two sides (which is what happens with a more
+               naive specification).
+          -->
+        <direct name="clbouts1" input="fle[3:0].out" output="clb.O"/>
+      </interconnect>
+      <!-- Every input pin is driven by 15% of the tracks in a channel, every output pin is driven by 10% of the tracks in a channel -->
+      <!-- Place this general purpose logic block in any unspecified column -->
+    </pb_type>
+    <!-- Define general purpose logic block (CLB) ends -->
+  </complexblocklist>
+</architecture>