diff --git a/piker/data/__init__.py b/piker/data/__init__.py
index 5459b4ba..e46db9b7 100644
--- a/piker/data/__init__.py
+++ b/piker/data/__init__.py
@@ -23,10 +23,13 @@ from ._sharedmem import (
     maybe_open_shm_array,
     attach_shm_array,
     open_shm_array,
-    SharedArray,
+    ShmArray,
     get_shm_token,
 )
-from ._buffer import incr_buffer
+from ._buffer import (
+    increment_ohlc_buffer,
+    subscribe_ohlc_for_increment
+)
 
 
 __all__ = [
@@ -35,7 +38,7 @@ __all__ = [
     'attach_shm_array',
     'open_shm_array',
     'get_shm_token',
-    'incr_buffer',
+    'subscribe_ohlc_for_increment',
 ]
 
 
@@ -115,7 +118,7 @@ class Feed:
     """
     name: str
     stream: AsyncIterator[Dict[str, Any]]
-    shm: SharedArray
+    shm: ShmArray
     _broker_portal: tractor._portal.Portal
     _index_stream: Optional[AsyncIterator[Dict[str, Any]]] = None
 
@@ -129,7 +132,7 @@ class Feed:
             # created for all practical purposes
             self._index_stream = await self._broker_portal.run(
                 'piker.data',
-                'incr_buffer',
+                'increment_ohlc_buffer',
                 shm_token=self.shm.token,
                 topics=['index'],
             )
diff --git a/piker/data/_buffer.py b/piker/data/_buffer.py
index 43be7dc0..5e1c3588 100644
--- a/piker/data/_buffer.py
+++ b/piker/data/_buffer.py
@@ -1,74 +1,99 @@
 """
 Data buffers for fast shared humpy.
 """
-from typing import Tuple, Callable
-import time
+from typing import Tuple, Callable, Dict
+# import time
 
 import tractor
 import trio
 
-from ._sharedmem import attach_shm_array
+from ._sharedmem import ShmArray
+
+
+_shms: Dict[int, ShmArray] = {}
 
 
 @tractor.msg.pub
-async def incr_buffer(
+async def increment_ohlc_buffer(
     shm_token: dict,
     get_topics: Callable[..., Tuple[str]],
     # delay_s: Optional[float] = None,
 ):
     """Task which inserts new bars into the provide shared memory array
     every ``delay_s`` seconds.
+
+    This task fulfills 2 purposes:
+    - it takes the subscribed set of shm arrays and increments them
+      on a common time period
+    - broadcast of this increment "signal" message to other actor
+      subscribers
+
+    Note that if **no** actor has initiated this task then **none** of
+    the underlying buffers will actually be incremented.
     """
-    # TODO: right now we'll spin printing bars if the last time
-    # stamp is before a large period of no market activity.
-    # Likely the best way to solve this is to make this task
-    # aware of the instrument's tradable hours?
-
-    shm = attach_shm_array(
-        token=shm_token,
-        readonly=False,
-    )
-
-    # determine ohlc delay between bars
-    # to determine time step between datums
-    times = shm.array['time']
-    delay_s = times[-1] - times[times != times[-1]][-1]
+    # TODO: right now we'll spin printing bars if the last time stamp is
+    # before a large period of no market activity.  Likely the best way
+    # to solve this is to make this task aware of the instrument's
+    # tradable hours?
 
     # adjust delay to compensate for trio processing time
-    ad = delay_s - 0.002
+    ad = min(_shms.keys()) - 0.001
 
-    async def sleep():
-        """Sleep until next time frames worth has passed from last bar.
-        """
-        # last_ts = shm.array[-1]['time']
-        # delay = max((last_ts + ad) - time.time(), 0)
-        # await trio.sleep(delay)
-        await trio.sleep(ad)
+    # async def sleep():
+    #     """Sleep until next time frames worth has passed from last bar.
+    #     """
+    #     # last_ts = shm.array[-1]['time']
+    #     # delay = max((last_ts + ad) - time.time(), 0)
+    #     # await trio.sleep(delay)
+    #     await trio.sleep(ad)
+
+    total_s = 0  # total seconds counted
+    lowest = min(_shms.keys())
+    ad = lowest - 0.001
 
     while True:
-        # sleep for duration of current bar
-        await sleep()
+        # TODO: do we want to support dynamically
+        # adding a "lower" lowest increment period?
+        await trio.sleep(ad)
+        total_s += lowest
 
-        # TODO: in theory we could make this faster by copying the
-        # "last" readable value into the underlying larger buffer's
-        # next value and then incrementing the counter instead of
-        # using ``.push()``?
+        # # sleep for duration of current bar
+        # await sleep()
 
-        # append new entry to buffer thus "incrementing" the bar
-        array = shm.array
-        last = array[-1:].copy()
-        (index, t, close) = last[0][['index', 'time', 'close']]
+        # increment all subscribed shm arrays
+        # TODO: this in ``numba``
+        for delay_s, shms in _shms.items():
+            if total_s % delay_s != 0:
+                continue
 
-        # this copies non-std fields (eg. vwap) from the last datum
-        last[
-            ['index', 'time', 'volume', 'open', 'high', 'low', 'close']
-        ][0] = (index + 1, t + delay_s, 0, close, close, close, close)
+            # TODO: numa this!
+            for shm in shms:
+                # TODO: in theory we could make this faster by copying the
+                # "last" readable value into the underlying larger buffer's
+                # next value and then incrementing the counter instead of
+                # using ``.push()``?
 
-        # write to the buffer
-        shm.push(last)
-        # print('incrementing array')
+                # append new entry to buffer thus "incrementing" the bar
+                array = shm.array
+                last = array[-1:].copy()
+                (index, t, close) = last[0][['index', 'time', 'close']]
 
-        # print(get_topics())
+                # this copies non-std fields (eg. vwap) from the last datum
+                last[
+                    ['index', 'time', 'volume', 'open', 'high', 'low', 'close']
+                ][0] = (index + 1, t + delay_s, 0, close, close, close, close)
+
+                # write to the buffer
+                shm.push(last)
 
         # broadcast the buffer index step
         yield {'index': shm._i.value}
+
+
+def subscribe_ohlc_for_increment(
+    shm: ShmArray,
+    delay: int,
+) -> None:
+    """Add an OHLC ``ShmArray`` to the increment set.
+    """
+    _shms.setdefault(delay, []).append(shm)
diff --git a/piker/data/_sharedmem.py b/piker/data/_sharedmem.py
index d6c53a95..6c410423 100644
--- a/piker/data/_sharedmem.py
+++ b/piker/data/_sharedmem.py
@@ -134,7 +134,7 @@ def _make_token(
     )
 
 
-class SharedArray:
+class ShmArray:
     def __init__(
         self,
         shmarr: np.ndarray,
@@ -216,7 +216,7 @@ def open_shm_array(
     size: int = int(2*60*60*10/5),
     dtype: np.dtype = base_ohlc_dtype,
     readonly: bool = False,
-) -> SharedArray:
+) -> ShmArray:
     """Open a memory shared ``numpy`` using the standard library.
 
     This call unlinks (aka permanently destroys) the buffer on teardown
@@ -245,7 +245,7 @@ def open_shm_array(
     )
     counter.value = 0
 
-    shmarr = SharedArray(
+    shmarr = ShmArray(
         array,
         counter,
         shm,
@@ -268,7 +268,7 @@ def attach_shm_array(
     size: int = int(60*60*10/5),
     # dtype: np.dtype = base_ohlc_dtype,
     readonly: bool = True,
-) -> SharedArray:
+) -> ShmArray:
     """Load and attach to an existing shared memory array previously
     created by another process using ``open_shared_array``.
     """
@@ -289,7 +289,7 @@ def attach_shm_array(
     # make sure we can read
     counter.value
 
-    sha = SharedArray(
+    sha = ShmArray(
         shmarr,
         counter,
         shm,
@@ -314,7 +314,7 @@ def maybe_open_shm_array(
     key: str,
     dtype: np.dtype = base_ohlc_dtype,
     **kwargs,
-) -> Tuple[SharedArray, bool]:
+) -> Tuple[ShmArray, bool]:
     """Attempt to attach to a shared memory block by a
     "key" determined by the users overall "system"
     (presumes you don't have the block's explicit token).