From 5a79c9bc09cfff496875c5b54a1f62348e4f6190 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Thu, 11 Jan 2018 11:38:06 +0800
Subject: [PATCH] RELEASE_NOTES: add SED

---
 RELEASE_NOTES.rst | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/RELEASE_NOTES.rst b/RELEASE_NOTES.rst
index 19f2e71b9..525455f53 100644
--- a/RELEASE_NOTES.rst
+++ b/RELEASE_NOTES.rst
@@ -3,9 +3,16 @@
 Release notes
 =============
 
-4.0 (unreleased)
-----------------
+4.0
+---
 
+* RTIO outputs use a new architecture called Scalable Event Dispatcher (SED),
+  which allows building systems with large number of RTIO channels more
+  efficiently.
+  From the user perspective, collision errors become asynchronous, and non-
+  monotonic timestamps on any combination of channels are generally allowed
+  (instead of producing sequence errors).
+  RTIO inputs are not affected.
 * The DDS channel number for the NIST CLOCK target has changed.
 * The dashboard configuration files are now stored one-per-master, keyed by the
   server address argument and the notify port.