diff --git a/bench/algorithm/coro-prime-sieve/4.nim b/bench/algorithm/coro-prime-sieve/4.nim
new file mode 100644
index 000000000..3444cb1fe
--- /dev/null
+++ b/bench/algorithm/coro-prime-sieve/4.nim
@@ -0,0 +1,91 @@
+import chronos
+import std/os
+import std/strutils
+
+
+
+##
+## # Channel[T]
+##
+## I craeted a very simple async-awaitable channel type so I can match the
+## reference Go implementation this benchmark originated from.
+##
+
+
+type Channel[T] = object
+  ## An simple one-item, async-awaitable Channel.
+  untilIsEmpty: Future[void]
+  untilIsFull: Future[void]
+  val: T
+
+
+proc newChannel[T](): ref Channel[T] =
+  ## Initializer. Allocate a new ref Channel object on the heap.
+  result = new Channel[T]
+  result[].untilIsEmpty = newFuture[void]()
+  result[].untilIsFull = newFuture[void]()
+  result[].untilIsEmpty.complete()
+
+
+proc send(chan: ref Channel[int], val: int) {.async.} =
+  # Accept val if empty, otherwise, suspend until empty.
+  await chan[].untilIsEmpty
+  chan[].untilIsEmpty = newFuture[void]()
+  chan[].val = val
+  chan[].untilIsFull.complete()
+
+
+proc recv[T](chan: ref Channel[T]): Future[T] {.async.} =
+  # Return held val if full, otherwise, suspend until full.
+  await chan[].untilIsFull
+  chan[].untilIsFull = newFuture[void]()
+  result = chan[].val
+  chan[].untilIsEmpty.complete()
+
+
+
+##
+## # Benchmark
+##
+## Below, "Concurrent Prime Sieve" that matches Go reference implementation.
+##
+##   [X] Uses coroutines.
+##   [X] Uses a coroutine scheduler.
+##   [X] Uses an async channel for communitating between coroutines.
+##   [X] Same 3 functions, structured like the reference.
+##
+
+
+proc generate(chan: ref Channel[int]) {.async.} =
+  ## Send the sequence 2, 3, 4, ... to cannel `chan`.
+  for i in 2 .. int.high:
+    await chan.send(i)
+
+
+proc filter(inChan, outChan: ref Channel[int], prime: int) {.async.} =
+  ## Copy the values from channel `inChan` to channel `outChan`, removing those
+  ## divisible by `prime`.
+  while true:
+    let i = await inChan.recv() # revieve value from `inChan`
+    if i mod prime != 0:
+      await outChan.send(i) # send `i` to `outChan`
+
+
+proc main(n: int) {.async.} =
+  ## The prime sieve: Daisy-chain filter processes.
+  var firstChan = newChannel[int]() # craete a new channel
+  asyncCheck generate(firstChan) # launch generate coroutine
+  for i in 0 ..< n:
+    let prime = await firstChan.recv()
+    echo prime
+    var secondChan = newChannel[int]()
+    asyncCheck filter(firstChan, secondChan, prime)
+    firstChan = secondChan
+
+
+when isMainModule:
+
+  let n = if paramCount() > 0: parseInt(paramStr(1)) else: 100
+  waitFor main(n)
+
+
diff --git a/bench/algorithm/coro-prime-sieve/5.nim b/bench/algorithm/coro-prime-sieve/5.nim
new file mode 100644
index 000000000..38a922c2a
--- /dev/null
+++ b/bench/algorithm/coro-prime-sieve/5.nim
@@ -0,0 +1,43 @@
+import chronos
+import std/os
+import std/strutils
+
+
+
+
+
+
+
+proc generate(chan: AsyncQueue[int]) {.async.} =
+  ## Send the sequence 2, 3, 4, ... to cannel `chan`.
+  for i in 2 .. int.high:
+    await chan.addFirst(i)
+
+
+proc filter(inChan, outChan: AsyncQueue[int], prime: int) {.async.} =
+  ## Copy the values from channel `inChan` to channel `outChan`, removing those
+  ## divisible by `prime`.
+  while true:
+    let i = await inChan.popLast() # revieve value from `inChan`
+    if i mod prime != 0:
+      await outChan.addFirst(i) # send `i` to `outChan`
+
+
+proc main(n: int) {.async.} =
+  ## The prime sieve: Daisy-chain filter processes.
+  var firstChan = newAsyncQueue[int](1) # craete a new channel
+  asyncCheck generate(firstChan) # launch generate coroutine
+  for i in 0 ..< n:
+    let prime = await firstChan.popLast()
+    echo prime
+    var secondChan = newAsyncQueue[int](1)
+    asyncCheck filter(firstChan, secondChan, prime)
+    firstChan = secondChan
+
+
+when isMainModule:
+
+  let n = if paramCount() > 0: parseInt(paramStr(1)) else: 100
+  waitFor main(n)
+
+
diff --git a/bench/algorithm/coro-prime-sieve/6.nim b/bench/algorithm/coro-prime-sieve/6.nim
new file mode 100644
index 000000000..53b16c352
--- /dev/null
+++ b/bench/algorithm/coro-prime-sieve/6.nim
@@ -0,0 +1,83 @@
+import yasync
+import chronos
+import std/os
+import std/strutils
+
+
+##
+## Channel implementation copied from the `yasync` repo, testcase `test7.nim`
+##
+
+type
+  Channel[T] = object
+    waitingCont: ptr Cont[T]
+    sendingCont: ptr Cont[void]
+    val: T
+
+proc send[T](c: var Channel[T], v: T, env: ptr Cont[void]) {.asyncRaw.} =
+  doAssert(c.sendingCont == nil, "Too many senders")
+  if c.waitingCont == nil:
+    c.val = v
+    c.sendingCont = env
+  else:
+    let cont = c.waitingCont
+    c.waitingCont = nil
+    cont.complete(v)
+    env.complete()
+
+proc recv[T](c: var Channel[T], env: ptr Cont[T]) {.asyncRaw.} =
+  doAssert(c.waitingCont == nil, "Too many receivers")
+  if c.sendingCont == nil:
+    c.waitingCont = env
+  else:
+    let cont = c.sendingCont
+    c.sendingCont = nil
+    env.complete(c.val)
+    cont.complete()
+
+proc newChannel[T](): ref Channel[T] =
+  new(result)
+
+
+##
+## # Benchmark
+##
+## Below, "Concurrent Prime Sieve" that matches Go reference implementation.
+##
+##   [X] Uses coroutines.
+##   [X] Uses a coroutine scheduler.
+##   [X] Uses an async channel for communitating between coroutines.
+##   [X] Same 3 functions, structured like the reference.
+##
+
+proc generate(chan: ref Channel[int]) {.yasync.async.} =
+  ## Send the sequence 2, 3, 4, ... to cannel `chan`.
+  for i in 2 .. int.high:
+    await chan[].send(i)
+
+proc filter(inChan, outChan: ref Channel[int], prime: int) {.yasync.async.} =
+  ## Copy the values from channel `inChan` to channel `outChan`, removing those
+  ## divisible by `prime`.
+  while true:
+    let i = await inChan[].recv() # revieve value from `inChan`
+    if i mod prime != 0:
+      await outChan[].send(i) # send `i` to `outChan`
+
+proc main(n: int) {.yasync.async.} =
+  ## The prime sieve: Daisy-chain filter processes.
+  var firstChan = newChannel[int]() # craete a new channel
+  discard generate(firstChan) # launch generate coroutine
+  for i in 0 ..< n:
+    let prime = await firstChan[].recv()
+    echo prime
+    var secondChan = newChannel[int]()
+    discard filter(firstChan, secondChan, prime)
+    firstChan = secondChan
+
+when isMainModule:
+
+  let n = if paramCount() > 0: parseInt(paramStr(1)) else: 100
+  var env: asyncCallEnvType(main(n))
+  asyncLaunchWithEnv(env, main(n))
+
+
diff --git a/bench/bench_nim.yaml b/bench/bench_nim.yaml
index d7f6049ce..a65929884 100644
--- a/bench/bench_nim.yaml
+++ b/bench/bench_nim.yaml
@@ -33,6 +33,8 @@ problems:
     source:
       - 1.nim
       - 3.nim
+      - 5.nim
+      - 6.nim
   - name: lru
     source:
       - 1.nim
@@ -60,7 +62,9 @@ environments:
     include: nim
     include_sub_dir:
     before_build:
-    build: nimble build app -y --mm:orc -d:danger --panics:on -d:nimCoroutines --threads:on --tlsEmulation:off --verbose
+      - nimble refresh
+      - nimble install --depsOnly
+    build: nimble cpp app -y --mm:orc -d:danger --panics:on -d:nimCoroutines --threads:on --tlsEmulation:off --passC=-march=native --passC=-mtune=native --passC=-flto --passC=-fwhole-program --passC=-ffp-contract=off --verbose 
     after_build:
       - cp app out
     out_dir: out
@@ -72,7 +76,9 @@ environments:
     include: nim
     include_sub_dir:
     before_build:
-    build: nimble build app -y --mm:orc --cc:clang -d:danger --panics:on -d:nimCoroutines --threads:on --tlsEmulation:off --verbose
+      - nimble refresh
+      - nimble install --depsOnly
+    build: nimble build app -y --mm:orc --cc:clang -d:danger --panics:on -d:nimCoroutines --threads:on --tlsEmulation:off --verbose 
     after_build:
       - cp app out
     out_dir: out
diff --git a/bench/include/nim/app.nimble b/bench/include/nim/app.nimble
index 7ba786267..667c043c7 100644
--- a/bench/include/nim/app.nimble
+++ b/bench/include/nim/app.nimble
@@ -10,3 +10,5 @@ bin           = @["app"]
 # Dependencies
 
 requires "nim >= 2.0.0"
+requires "chronos"
+requires "yasync"