diff --git a/pipelined/src/ieu/comparator.sv b/pipelined/src/ieu/comparator.sv
index bc5a9a288..cc2eb1723 100644
--- a/pipelined/src/ieu/comparator.sv
+++ b/pipelined/src/ieu/comparator.sv
@@ -71,7 +71,7 @@ module comparator #(parameter WIDTH=64) (
   assign flags = {eq, lt, ltu};
 endmodule
 
-// This comaprator 
+// This comaprator is best
 module comparator_dc_flip #(parameter WIDTH=64) (
   input  logic [WIDTH-1:0] a, b,
   input  logic             sgnd,
diff --git a/pipelined/src/ppa/ppa.sv b/pipelined/src/ppa/ppa.sv
index de0bac321..f1712d291 100644
--- a/pipelined/src/ppa/ppa.sv
+++ b/pipelined/src/ppa/ppa.sv
@@ -31,36 +31,318 @@ module ppa_inv(input a, output y);
 endmodule
  */
 
-module ppa_add #(parameter WIDTH=8) (
-    input logic [7:0] a, b,
-    output logic [7:0] y
+module ppa_comparator_16 #(parameter WIDTH=16) (
+  input  logic [WIDTH-1:0] a, b,
+  input  logic             sgnd,
+  output logic [1:0]       flags);
+
+  ppa_comparator #(WIDTH) comp (.*);
+endmodule
+
+module ppa_comparator_32 #(parameter WIDTH=32) (
+  input  logic [WIDTH-1:0] a, b,
+  input  logic             sgnd,
+  output logic [1:0]       flags);
+
+  ppa_comparator #(WIDTH) comp (.*);
+endmodule
+
+module ppa_comparator_64 #(parameter WIDTH=64) (
+  input  logic [WIDTH-1:0] a, b,
+  input  logic             sgnd,
+  output logic [1:0]       flags);
+
+  ppa_comparator #(WIDTH) comp (.*);
+endmodule
+
+
+ module ppa_comparator #(parameter WIDTH=16) (
+  input  logic [WIDTH-1:0] a, b,
+  input  logic             sgnd,
+  output logic [1:0]       flags);
+
+  logic eq, lt, ltu;
+  logic [WIDTH-1:0] af, bf;
+
+  // For signed numbers, flip most significant bit
+  assign af = {a[WIDTH-1] ^ sgnd, a[WIDTH-2:0]};
+  assign bf = {b[WIDTH-1] ^ sgnd, b[WIDTH-2:0]};
+
+  // behavioral description gives best results
+  assign eq = (af == bf);
+  assign lt = (af < bf);
+  assign flags = {eq, lt};
+endmodule
+
+
+module ppa_add_32 #(parameter WIDTH=32) (
+    input logic [WIDTH-1:0] a, b,
+    output logic [WIDTH-1:0] y
 );
 
-   assign out = a + b;
+   assign y = a + b;
+endmodule
+
+module ppa_add_64 #(parameter WIDTH=64) (
+    input logic [WIDTH-1:0] a, b,
+    output logic [WIDTH-1:0] y
+);
+
+   assign y = a + b;
 endmodule
 
 
-/*module inv4(input logic a, output logic y);
-  logic [3:0] b
-  INVX2 i0(a, b[0]);
-  INVX2 i1(a, b[1]);
-  INVX2 i2(a, b[2]);
-  INVX2 i3(a, b[3]);
-  INVX2 i00(b[0], y;
-  INVX2 i01(b[0], y);
-  INVX2 i02(b[0], y);
-  INVX2 i03(b[0], y);
-  INVX2 i10(b[1], y;
-  INVX2 i11(b[1], y);
-  INVX2 i12(b[1], y);
-  INVX2 i13(b[1], y);
-  INVX2 i20(b[2], y;
-  INVX2 i21(b[2], y);
-  INVX2 i22(b[2], y);
-  INVX2 i23(b[2], y);
-  INVX2 i30(b[3], y;
-  INVX2 i31(b[3], y);
-  INVX2 i32(b[3], y);
-  INVX2 i33(b[3], y);
+module ppa_add_16 #(parameter WIDTH=16) (
+    input logic [WIDTH-1:0] a, b,
+    output logic [WIDTH-1:0] y
+);
+
+   assign y = a + b;
 endmodule
-*/
+
+module ppa_shiftleft(
+  assign y = a << amt;
+)
+
+module ppa_mult(
+  assign y = a * b;
+)
+
+module ppa_alu #(parameter WIDTH=32) (
+  input  logic [WIDTH-1:0] A, B,
+  input  logic [2:0]       ALUControl,
+  input  logic [2:0]       Funct3,
+  output logic [WIDTH-1:0] Result,
+  output logic [WIDTH-1:0] Sum);
+
+  logic [WIDTH-1:0] CondInvB, Shift, SLT, SLTU, FullResult;
+  logic        Carry, Neg;
+  logic        LT, LTU;
+  logic        W64, SubArith, ALUOp;
+  logic [2:0]  ALUFunct;
+  logic        Asign, Bsign;
+
+  // Extract control signals
+  // W64 indicates RV64 W-suffix instructions acting on lower 32-bit word
+  // SubArith indicates subtraction
+  // ALUOp = 0 for address generation addition or 1 for regular ALU
+  assign {W64, SubArith, ALUOp} = ALUControl;
+
+  // addition
+  assign CondInvB = SubArith ? ~B : B;
+  assign {Carry, Sum} = A + CondInvB + {{(WIDTH-1){1'b0}}, SubArith};
+  
+  // Shifts
+  shifter sh(.A, .Amt(B[`LOG_XLEN-1:0]), .Right(Funct3[2]), .Arith(SubArith), .W64, .Y(Shift));
+
+  // condition code flags based on subtract output Sum = A-B
+  // Overflow occurs when the numbers being subtracted have the opposite sign 
+  // and the result has the opposite sign of A
+  assign Neg  = Sum[WIDTH-1];
+  assign Asign = A[WIDTH-1];
+  assign Bsign = B[WIDTH-1];
+  assign LT = Asign & ~Bsign | Asign & Neg | ~Bsign & Neg; // simplified from Overflow = Asign & Bsign & Asign & Neg; LT = Neg ^ Overflow
+  assign LTU = ~Carry;
+ 
+  // SLT
+  assign SLT = {{(WIDTH-1){1'b0}}, LT};
+  assign SLTU = {{(WIDTH-1){1'b0}}, LTU};
+ 
+  // Select appropriate ALU Result
+  assign ALUFunct = Funct3 & {3{ALUOp}}; // Force ALUFunct to 0 to Add when ALUOp = 0
+  always_comb
+    casez (ALUFunct)
+      3'b000: FullResult = Sum;       // add or sub
+      3'b?01: FullResult = Shift;     // sll, sra, or srl
+      3'b010: FullResult = SLT;       // slt
+      3'b011: FullResult = SLTU;      // sltu
+      3'b100: FullResult = A ^ B;     // xor
+      3'b110: FullResult = A | B;     // or 
+      3'b111: FullResult = A & B;     // and
+    endcase
+
+  // support W-type RV64I ADDW/SUBW/ADDIW/Shifts that sign-extend 32-bit result to 64 bits
+  if (WIDTH==64)  assign Result = W64 ? {{32{FullResult[31]}}, FullResult[31:0]} : FullResult;
+  else            assign Result = FullResult;
+endmodule
+
+
+
+module ppa_shifter (
+  input  logic [`XLEN-1:0]     A,
+  input  logic [`LOG_XLEN-1:0] Amt,
+  input  logic                 Right, Arith, W64,
+  output logic [`XLEN-1:0]     Y);
+
+  logic [2*`XLEN-2:0]      z, zshift;
+  logic [`LOG_XLEN-1:0]    amttrunc, offset;
+
+  // Handle left and right shifts with a funnel shifter.
+  // For RV32, only 32-bit shifts are needed.   
+  // For RV64, 32 and 64-bit shifts are needed, with sign extension.
+
+  // funnel shifter input (see CMOS VLSI Design 4e Section 11.8.1, note Table 11.11 shift types wrong)
+  if (`XLEN==32) begin:shifter // RV32
+    always_comb  // funnel mux
+      if (Right) 
+        if (Arith) z = {{31{A[31]}}, A};
+        else       z = {31'b0, A};
+      else         z = {A, 31'b0};
+    assign amttrunc = Amt; // shift amount
+  end else begin:shifter  // RV64
+    always_comb  // funnel mux
+      if (W64) begin // 32-bit shifts
+        if (Right)
+          if (Arith) z = {64'b0, {31{A[31]}}, A[31:0]};
+          else       z = {95'b0, A[31:0]};
+        else         z = {32'b0, A[31:0], 63'b0};
+      end else begin
+        if (Right)
+          if (Arith) z = {{63{A[63]}}, A};
+          else       z = {63'b0, A};
+        else         z = {A, 63'b0};         
+      end
+    assign amttrunc = W64 ? {1'b0, Amt[4:0]} : Amt; // 32 or 64-bit shift
+  end
+
+  // opposite offset for right shfits
+  assign offset = Right ? amttrunc : ~amttrunc;
+  
+  // funnel operation
+  assign zshift = z >> offset;
+  assign Y = zshift[`XLEN-1:0];    
+endmodule
+
+module ppa_prioritythermometer #(parameter N = 8) (
+  input  logic  [N-1:0] a,
+  output logic  [N-1:0] y
+);
+
+// Carefully crafted so design compiler will synthesize into a fast tree structure
+//  Rather than linear.
+
+  // create thermometer code mask
+  genvar i;
+  assign y[0] = ~a[0];
+  for (i=1; i<N; i++) begin:therm
+    assign y[i] = y[i-1] & ~a[i];
+  end
+endmodule
+
+
+
+module ppa_priorityonehot #(parameter N = 8) (
+  input  logic  [N-1:0] a,
+  output logic  [N-1:0] y
+);
+  logic [N-1:0] nolower;
+
+  // create thermometer code mask
+  ppa_prioritythermometer #(N) maskgen(.a({a[N-2:0], 1'b0}), .y(nolower));
+  assign y = a & nolower;
+endmodule
+
+module ppa_prioriyencoder #(parameter N = 8) (
+  input  logic  [N-1:0] a,
+  output logic  [$clog2(N)-1:0] y
+);
+// Carefully crafted so design compiler will synthesize into a fast tree structure
+//  Rather than linear.
+
+  // create thermometer code mask
+  genvar i;
+  for (i=0; i<N; i++) begin:pri
+    if (a[i]) y= i;
+  end
+endmodule
+
+module decoder
+  input  logic  [$clog2(N)-1:0] a,
+  output logic  [N-1:0] y
+  always_comb begin 
+    y = 0;
+    y[a] = 1;
+  end
+
+module mux2 #(parameter WIDTH = 8) (
+  input  logic [WIDTH-1:0] d0, d1, 
+  input  logic             s, 
+  output logic [WIDTH-1:0] y);
+
+  assign y = s ? d1 : d0; 
+endmodule
+
+module mux3 #(parameter WIDTH = 8) (
+  input  logic [WIDTH-1:0] d0, d1, d2,
+  input  logic [1:0]       s, 
+  output logic [WIDTH-1:0] y);
+
+  assign y = s[1] ? d2 : (s[0] ? d1 : d0); 
+endmodule
+
+module mux4 #(parameter WIDTH = 8) (
+  input  logic [WIDTH-1:0] d0, d1, d2, d3,
+  input  logic [1:0]       s, 
+  output logic [WIDTH-1:0] y);
+
+  assign y = s[1] ? (s[0] ? d3 : d2) : (s[0] ? d1 : d0); 
+endmodule
+
+module mux6 #(parameter WIDTH = 8) (
+  input  logic [WIDTH-1:0] d0, d1, d2, d3, d4, d5,
+  input  logic [2:0]       s, 
+  output logic [WIDTH-1:0] y);
+
+  assign y = s[2] ? (s[0] ? d5 : d4) : (s[1] ? (s[0] ? d3 : d2) : (s[0] ? d1 : d0)); 
+endmodule
+
+module mux8 #(parameter WIDTH = 8) ( *** add inputs
+  input  logic [WIDTH-1:0] d0, d1, d2, d3, d4, d5, 
+  input  logic [2:0]       s, 
+  output logic [WIDTH-1:0] y);
+
+  assign y = s[2] ? (s[0] ? d5 : d4) : (s[1] ? (s[0] ? d3 : d2) : (s[0] ? d1 : d0)); 
+endmodule
+
+// *** some way to express data-critical inputs
+
+module flop #(parameter WIDTH = 8) ( 
+  input  logic             clk,
+  input  logic [WIDTH-1:0] d, 
+  output logic [WIDTH-1:0] q);
+
+  always_ff @(posedge clk)
+    q <= #1 d;
+endmodule
+
+module flopr #(parameter WIDTH = 8) ( 
+  input  logic             clk, reset,
+  input  logic [WIDTH-1:0] d, 
+  output logic [WIDTH-1:0] q);
+
+  always_ff @(posedge clk)
+    if (reset) q <= #1 0;
+    else       q <= #1 d;
+endmodule
+
+module floprasynnc #(parameter WIDTH = 8) ( 
+  input  logic             clk, reset,
+  input  logic [WIDTH-1:0] d, 
+  output logic [WIDTH-1:0] q);
+
+  always_ff @(posedge clk or posedge reset)
+    if (reset) q <= #1 0;
+    else       q <= #1 d;
+endmodule
+
+module flopenr #(parameter WIDTH = 8) (
+  input  logic             clk, reset, en,
+  input  logic [WIDTH-1:0] d, 
+  output logic [WIDTH-1:0] q);
+
+  always_ff @(posedge clk)
+    if (reset)   q <= #1 0;
+    else if (en) q <= #1 d;
+endmodule
+
+
diff --git a/synthDC/ppa b/synthDC/ppa
new file mode 100755
index 000000000..5929ca956
--- /dev/null
+++ b/synthDC/ppa
@@ -0,0 +1,28 @@
+#!/bin/bash
+# David_Harris@hmc.edu and Madeleine Masser-Frye 11 May 2022
+# Run PPA experiments on different modules
+rm -rf runs/ppa*
+make synth DESIGN=ppa_add_16 TECH=sky90 DRIVE=INV FREQ=10 MAXOPT=1 &
+make synth DESIGN=ppa_add_32 TECH=sky90 DRIVE=INV FREQ=1 MAXOPT=10 &
+make synth DESIGN=ppa_add_64 TECH=sky90 DRIVE=INV FREQ=10 MAXOPT=1 &
+make synth DESIGN=ppa_add_16 TECH=sky90 DRIVE=INV FREQ=4000 MAXOPT=1 &
+make synth DESIGN=ppa_add_32 TECH=sky90 DRIVE=INV FREQ=4000 MAXOPT=1 &
+make synth DESIGN=ppa_add_64 TECH=sky90 DRIVE=INV FREQ=4000 MAXOPT=1 &
+make synth DESIGN=ppa_add_16 TECH=sky90 DRIVE=INV FREQ=5000 MAXOPT=1 &
+make synth DESIGN=ppa_add_32 TECH=sky90 DRIVE=INV FREQ=5000 MAXOPT=1 &
+make synth DESIGN=ppa_add_64 TECH=sky90 DRIVE=INV FREQ=5000 MAXOPT=1 &
+make synth DESIGN=ppa_add_16 TECH=sky90 DRIVE=INV FREQ=6000 MAXOPT=1 &
+make synth DESIGN=ppa_add_32 TECH=sky90 DRIVE=INV FREQ=6000 MAXOPT=1 &
+make synth DESIGN=ppa_add_64 TECH=sky90 DRIVE=INV FREQ=6000 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_16 TECH=sky90 DRIVE=INV FREQ=10 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_32 TECH=sky90 DRIVE=INV FREQ=10 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_64 TECH=sky90 DRIVE=INV FREQ=10 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_16 TECH=sky90 DRIVE=INV FREQ=8000 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_32 TECH=sky90 DRIVE=INV FREQ=8000 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_64 TECH=sky90 DRIVE=INV FREQ=8000 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_16 TECH=sky90 DRIVE=INV FREQ=10000 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_32 TECH=sky90 DRIVE=INV FREQ=10000 MAXOPT=1 &
+make synth DESIGN=ppa_comparator_64 TECH=sky90 DRIVE=INV FREQ=10000 MAXOPT=1 &
+wait 
+grep "Critical Path Length" runs/ppa_*/reports/*qor*
+grep "Design Area" runs/ppa_*/reports/*qor*
diff --git a/synthDC/scripts/synth.tcl b/synthDC/scripts/synth.tcl
index 3feb5f123..9d6aac68a 100755
--- a/synthDC/scripts/synth.tcl
+++ b/synthDC/scripts/synth.tcl
@@ -120,8 +120,8 @@ if {$tech == "sky130"} {
 }
 
 # Set input/output delay
-set_input_delay 0.1 -max -clock $my_clk $all_in_ex_clk
-set_output_delay 0.1 -max -clock $my_clk [all_outputs]
+set_input_delay 0.0 -max -clock $my_clk $all_in_ex_clk
+set_output_delay 0.0 -max -clock $my_clk [all_outputs]
 
 # Setting load constraint on output ports 
 if {$tech == "sky130"} {