diff --git a/bayeux.cabal b/bayeux.cabal
index b143ff0..f816982 100644
--- a/bayeux.cabal
+++ b/bayeux.cabal
@@ -30,6 +30,7 @@ library
                     , Bayeux.Ice40.Spi
                     , Bayeux.Ice40.Spram
                     , Bayeux.Lp
+                    , Bayeux.Queue
                     , Bayeux.Rtl
                     , Bayeux.Signal
                     , Bayeux.Tableaux
diff --git a/lib/Bayeux/Queue.hs b/lib/Bayeux/Queue.hs
new file mode 100644
index 0000000..6598b1f
--- /dev/null
+++ b/lib/Bayeux/Queue.hs
@@ -0,0 +1,95 @@
+{-# LANGUAGE RankNTypes          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
+module Bayeux.Queue
+  ( MonadQueue(..)
+  ) where
+
+import Bayeux.Encode
+import Bayeux.Rtl (Rtl)
+import Bayeux.Signal
+import Bayeux.Width
+import Data.Array
+import Data.Finite
+import Data.Proxy
+import GHC.TypeNats
+
+class MonadQueue m where
+  queue :: Width a
+        => Natural       -- ^ size
+        -> Sig (Maybe a) -- ^ enqueue
+        -> Sig Bool      -- ^ dequeue
+        -> m (Sig (Maybe a))
+
+instance MonadQueue Rtl where
+  queue sz = withNat sz queue'
+
+
+withNat :: forall r. Natural -> (forall n. KnownNat n => SNat n -> r) -> r
+withNat n f = withSomeSNat n go
+  where
+    go :: forall m. SNat m -> r
+    go sm = withKnownNat sm $ f sm
+
+data Queue n a = Queue
+  { rPtr   :: Finite n
+  , rWrap  :: Bool
+  , wPtr   :: Finite n
+  , wWrap  :: Bool
+  , dArray :: Array (Finite n) a
+  }
+  deriving (Eq, Read, Show)
+
+instance (KnownNat n, Width a) => Width (Queue n a) where
+  width _ = 2 + sum
+    [ 2 * width (undefined :: Finite n)
+    , width (undefined :: Array (Finite n) a)
+    ]
+
+instance (KnownNat n, Encode a) => Encode (Queue n a) where
+  encode q = mconcat
+    [ encode $ rPtr   q
+    , encode $ rWrap  q
+    , encode $ wPtr   q
+    , encode $ wWrap  q
+    , encode $ dArray q
+    ]
+
+sliceRPtr :: Sig (Queue n a) -> Sig (Finite n)
+sliceRPtr = slice (width (undefined :: Finite n) + base - 1) base
+  where
+    base = width (undefined :: Finite n) - 1 + dArrayWidth + 3
+
+sliceRWrap :: Sig (Queue n a) -> Sig Bool
+sliceRWrap = slice
+  (width (undefined :: Finite n) - 1 + dArrayWidth + 2)
+  (width (undefined :: Finite n) - 1 + dArrayWidth + 2)
+
+rWrapBase :: forall n. KnownNat n => Proxy n -> Integer
+rWrapBase _ = width (undefined :: Finite n) - 1 + dArrayWidth (Proxy :: Proxy n) + 2
+
+sliceWPtr :: forall n a. KnownNat n => Sig (Queue n a) -> Sig (Finite n)
+sliceWPtr = slice
+  (width (undefined :: Finite n) - 1 + dArrayWidth (Proxy :: Proxy n) + 1)
+  (dArrayWidth (Proxy :: Proxy n) + 1)
+
+sliceWWrap :: forall n a. KnownNat n => Sig (Queue n a) -> Sig Bool
+sliceWWrap = slice (dArrayWidth (Proxy :: Proxy n)) (dArrayWidth (Proxy :: Proxy n))
+
+sliceDArray :: forall n a. KnownNat n => Sig (Queue n a) -> Sig (Array (Finite n) a)
+sliceDArray = slice (dArrayWidth (Proxy :: Proxy n) - 1) 0
+
+dArrayWidth :: forall n. KnownNat n => Proxy n -> Integer
+dArrayWidth _ = width (undefined :: Array (Finite n) a)
+
+queue'
+  :: forall n a
+   . KnownNat n
+  => Width a
+  => SNat n
+  -> Sig (Maybe a)
+  -> Sig Bool
+  -> Rtl (Sig (Maybe a))
+queue' _ enqM deq = do
+  s <- process $ \(s :: Sig (Queue n a)) -> undefined
+  return $ Sig undefined