diff --git a/hbs2-peer/app/BlockDownloadNew.hs b/hbs2-peer/app/BlockDownloadNew.hs
index 38de17d7..984adc5a 100644
--- a/hbs2-peer/app/BlockDownloadNew.hs
+++ b/hbs2-peer/app/BlockDownloadNew.hs
@@ -6,19 +6,13 @@
 module BlockDownloadNew where
 
 import HBS2.Prelude.Plated
-import HBS2.Clock
 import HBS2.OrDie
 import HBS2.Data.Detect
 import HBS2.Hash
-import HBS2.Merkle
 import HBS2.Defaults
 import HBS2.Events
 import HBS2.Net.Proto.Service
 import HBS2.Net.Proto.Sessions
-import HBS2.Data.Bundle
-import HBS2.Data.Types.SignedBox
-
-import HBS2.Base58
 import HBS2.Data.Types.Peer
 import HBS2.Data.Types.Refs
 import HBS2.Actors.Peer
@@ -29,18 +23,10 @@ import HBS2.Peer.Brains
 import HBS2.Storage
 import HBS2.Storage.Operations.Missed
 import HBS2.Misc.PrettyStuff
-import HBS2.Clock
-import HBS2.Net.Auth.Schema
-
-import HBS2.Peer.RPC.Internal.Types
-import HBS2.Peer.RPC.API.Peer
-
-import HBS2.Net.Messaging.TCP
 
 import PeerTypes
 import PeerInfo
 
-import Control.Monad.Trans.Maybe
 import Control.Monad.Trans.Cont
 import Control.Concurrent.STM (flushTQueue,retry)
 import Data.Map qualified as Map
@@ -52,9 +38,6 @@ import Data.HashMap.Strict qualified as HM
 import Data.HashSet (HashSet)
 import Data.HashSet qualified as HS
 import Data.IntMap qualified as IntMap
-import Data.IntMap (IntMap)
-import Data.List.Split qualified as Split
-import Data.Text qualified as Text
 import Data.Either
 import Data.Maybe
 import Data.ByteString.Lazy qualified as LBS
@@ -66,14 +49,12 @@ import Data.List qualified as L
 import Data.Coerce
 import Numeric
 import UnliftIO
-import Control.Concurrent.STM qualified as STM
+import Control.Concurrent.STM.TSem (TSem)
+import Control.Concurrent.STM.TSem qualified as TSem
 import UnliftIO.Concurrent
-import System.Random
+import UnliftIO.STM
 import Lens.Micro.Platform
 
-import System.Random qualified as R
-import System.Random.Shuffle qualified as Shuffle
-
 import Streaming.Prelude qualified as S
 
 
@@ -570,7 +551,7 @@ downloadDispatcher :: forall e m . ( e ~ L4Proto
                  -> m ()
 downloadDispatcher brains env = flip runContT pure do
 
-  pts   <- newTVarIO ( mempty :: HashMap (Peer e) (Async ()) )
+  pts   <- newTVarIO ( mempty :: HashMap (Peer e) (Async (), PeerNonce) )
   -- tasks <- newTVarIO ( HPSQ.empty :: HashPSQ (Work e) Double (TVar Int) )
 
   _blkNum   <- newTVarIO 0
@@ -635,28 +616,53 @@ downloadDispatcher brains env = flip runContT pure do
     manageThreads onBlock wip pts = do
       _pnum <- newTVarIO 1
 
+      _psem <- newTVarIO ( mempty :: HashMap PeerNonce TSem )
+
       forever $ (>> pause @'Seconds 10) $ withPeerM env do
         debug "MANAGE THREADS"
 
-        peers <- getKnownPeers @e <&> HS.fromList
+        peers <- HM.fromList <$> do
+                  pips <- getKnownPeers @e <&> HS.fromList
+                  S.toList_ $ for_ pips $ \p -> do
+                     mpd <- lift $ find  (KnownPeerKey p) id
+                     maybe1 mpd (pure ()) $
+                        \PeerData{..} -> S.yield (p, _peerOwnNonce)
 
-        for_ peers $ \p -> do
+
+        for_ (HM.toList peers) $ \(p,nonce) -> do
           here <- readTVarIO pts <&> HM.member p
-          i <- atomically $ stateTVar _pnum (\i -> (i, succ i))
+
+          (i,sem) <- atomically do
+                       j <- stateTVar _pnum (\i -> (i, succ i))
+                       psem <- readTVar _psem
+
+                       ssem <- case HM.lookup nonce psem of
+                         Just s -> pure s
+                         Nothing -> do
+                          -- TODO: semaphore-hardcode
+                          new <- TSem.newTSem 2
+                          modifyTVar _psem (HM.insert nonce new)
+                          pure new
+
+                       pure (j,ssem)
+
           unless here do
-            a <- async (peerThread i onBlock p wip)
-            atomically $ modifyTVar pts (HM.insert p a)
+            a <- async (peerThread sem i onBlock p wip)
+            atomically $ modifyTVar pts (HM.insert p (a,nonce))
 
         loosers <- atomically do
           xs <- readTVar pts <&> HM.toList
           -- FIXME: filter-stopped-tasks
-          let (alive,dead) = L.partition ( \(x,_) -> HS.member x peers ) xs
+          let (alive,dead) = L.partition ( \(x,_) -> HM.member x peers ) xs
           writeTVar pts (HM.fromList alive)
           pure dead
 
-        mapM_ cancel (fmap snd loosers)
+        for_ loosers $ \(p, (a, nonce)) -> do
+          cancel a
+          atomically do
+            modifyTVar _psem (HM.delete nonce)
 
-    peerThread me onBlock p wip = flip runContT pure do
+    peerThread sem me onBlock p wip = flip runContT pure do
 
       btimes <- newTVarIO ( mempty :: [Double] )
 
@@ -704,6 +710,7 @@ downloadDispatcher brains env = flip runContT pure do
           PChoose -> do
 
             what <- atomically do
+                     TSem.waitTSem sem
                      r <- newTVar ( HPSQ.empty @HashRef @Double @DCB )
                      blocks <- readTVar wip <&> HM.toList
                      let todo = blocks
@@ -799,7 +806,7 @@ downloadDispatcher brains env = flip runContT pure do
 
                 avg <- readTVarIO _avg
 
-                when (dtsec > avg) do
+                when (dtsec > avg * 1.15) do
                   burstMachineAddErrors bm 1
 
                 atomically do
@@ -818,6 +825,7 @@ downloadDispatcher brains env = flip runContT pure do
 
           PReleaseBlock hx dcb done -> do
             atomically do
+              TSem.signalTSem sem
               if not done  then do
                 modifyTVar (dcbBusy dcb) pred
               else do