diff --git a/src/kyupy/logic_sim.py b/src/kyupy/logic_sim.py
index dd9a45c..a8bc535 100644
--- a/src/kyupy/logic_sim.py
+++ b/src/kyupy/logic_sim.py
@@ -10,7 +10,7 @@ import math
 
 import numpy as np
 
-from . import logic, hr_bytes
+from . import numba, logic, hr_bytes, sim
 from .sim import SimOps, SimPrim
 
 
@@ -148,7 +148,7 @@ class LogicSim(SimOps):
 
         # return responses
 
-    def c_prop(self, inject_cb=None):
+    def c_prop(self, sims=None, inject_cb=None):
         """Propagate the input values towards the outputs (Perform all logic operations in topological order).
 
         If the circuit is sequential (it contains flip-flops), one call simulates one clock cycle.
@@ -168,20 +168,24 @@ class LogicSim(SimOps):
             resumes with the manipulated values after the callback returns.
         :type inject_cb: ``f(Line, ndarray)``
         """
+        if sims is None: sims = self.sims
+        nbytes = (sims - 1) // 8 + 1
         if self.m == 2:
-            for op, o0, i0, i1, i2, i3 in self.ops:
-                o0, i0, i1, i2, i3 = [self.vat[x,0] for x in (o0, i0, i1, i2, i3)]
-                if op == SimPrim.BUF1: self.c[o0]=self.c[i0]
-                elif op == SimPrim.INV1: self.c[o0] = ~self.c[i0]
-                elif op == SimPrim.AND2: self.c[o0] = self.c[i0] & self.c[i1]
-                elif op == SimPrim.NAND2: self.c[o0] = ~(self.c[i0] & self.c[i1])
-                elif op == SimPrim.OR2: self.c[o0] = self.c[i0] | self.c[i1]
-                elif op == SimPrim.NOR2: self.c[o0] = ~(self.c[i0] | self.c[i1])
-                elif op == SimPrim.XOR2: self.c[o0] = self.c[i0] ^ self.c[i1]
-                elif op == SimPrim.XNOR2: self.c[o0] = ~(self.c[i0] ^ self.c[i1])
-                else: print(f'unknown SimPrim {op}')
-                if inject_cb is not None: inject_cb(o0, self.s[o0])
-            pass
+            if inject_cb is None:
+                _prop_cpu(self.ops, self.vat, self.c[...,:nbytes])
+            else:
+                for op, o0, i0, i1, i2, i3 in self.ops:
+                    o0, i0, i1, i2, i3 = [self.vat[x,0] for x in (o0, i0, i1, i2, i3)]
+                    if op == SimPrim.BUF1: self.c[o0]=self.c[i0]
+                    elif op == SimPrim.INV1: self.c[o0] = ~self.c[i0]
+                    elif op == SimPrim.AND2: self.c[o0] = self.c[i0] & self.c[i1]
+                    elif op == SimPrim.NAND2: self.c[o0] = ~(self.c[i0] & self.c[i1])
+                    elif op == SimPrim.OR2: self.c[o0] = self.c[i0] | self.c[i1]
+                    elif op == SimPrim.NOR2: self.c[o0] = ~(self.c[i0] | self.c[i1])
+                    elif op == SimPrim.XOR2: self.c[o0] = self.c[i0] ^ self.c[i1]
+                    elif op == SimPrim.XNOR2: self.c[o0] = ~(self.c[i0] ^ self.c[i1])
+                    else: print(f'unknown SimPrim {op}')
+                    inject_cb(o0, self.s[o0])
         elif self.m == 4:
             pass
         else:
@@ -285,4 +289,18 @@ class LogicSim(SimOps):
     # def aoi21_fct(self, inputs, outputs):
     #     logic.bp_and(self.tmp[0], inputs[0], inputs[1])
     #     logic.bp_or(outputs[0], self.tmp[0], inputs[2])
-    #     logic.bp_not(outputs[0], outputs[0])
\ No newline at end of file
+    #     logic.bp_not(outputs[0], outputs[0])
+
+@numba.njit()
+def _prop_cpu(ops, vat, c):
+    for op, o0, i0, i1, i2, i3 in ops:
+        o0, i0, i1, i2, i3 = [vat[x,0] for x in (o0, i0, i1, i2, i3)]
+        if op == sim.BUF1: c[o0]=c[i0]
+        elif op == sim.INV1: c[o0] = ~c[i0]
+        elif op == sim.AND2: c[o0] = c[i0] & c[i1]
+        elif op == sim.NAND2: c[o0] = ~(c[i0] & c[i1])
+        elif op == sim.OR2: c[o0] = c[i0] | c[i1]
+        elif op == sim.NOR2: c[o0] = ~(c[i0] | c[i1])
+        elif op == sim.XOR2: c[o0] = c[i0] ^ c[i1]
+        elif op == sim.XNOR2: c[o0] = ~(c[i0] ^ c[i1])
+        else: print(f'unknown SimPrim {op}')
diff --git a/src/kyupy/sim.py b/src/kyupy/sim.py
index 76efe98..f0a9116 100644
--- a/src/kyupy/sim.py
+++ b/src/kyupy/sim.py
@@ -4,6 +4,43 @@ from bisect import bisect, insort_left
 
 import numpy as np
 
+BUF1 = 0b1010_1010_1010_1010
+INV1 = 0b0101_0101_0101_0101
+
+NAND4 = 0b0111_1111_1111_1111
+NAND3 = 0b0111_1111_0111_1111
+NAND2 = 0b0111_0111_0111_0111
+
+NOR4 = 0b0000_0000_0000_0001
+NOR3 = 0b0000_0001_0000_0001
+NOR2 = 0b0001_0001_0001_0001
+
+AND4 = 0b1000_0000_0000_0000
+AND3 = 0b1000_0000_1000_0000
+AND2 = 0b1000_1000_1000_1000
+
+OR4 = 0b1111_1111_1111_1110
+OR3 = 0b1111_1110_1111_1110
+OR2 = 0b1110_1110_1110_1110
+
+XOR4 = 0b0110_1001_1001_0110
+XOR3 = 0b1001_0110_1001_0110
+XOR2 = 0b0110_0110_0110_0110
+
+XNOR4 = 0b1001_0110_0110_1001
+XNOR3 = 0b0110_1001_0110_1001
+XNOR2 = 0b1001_1001_1001_1001
+
+AO22 = 0b1111_1000_1000_1000
+AOI22 = 0b0000_0111_0111_0111
+AO21 = 0b1110_1010_1110_1010
+AOI21 = 0b0001_0101_0001_0101
+OA22 = 0b1110_1110_1110_0000
+OAI22 = 0b0001_0001_0001_1111
+OA21 = 0b1010_1000_1010_1000
+OAI21 = 0b0101_0111_0101_0111
+MUX21 = 0b1110_0100_1110_0100
+
 class SimPrim:
     BUF1 = 0b1010_1010_1010_1010
     INV1 = 0b0101_0101_0101_0101