diff --git a/docs/startup.md b/docs/startup.md
index b33832894..ad8e84df7 100644
--- a/docs/startup.md
+++ b/docs/startup.md
@@ -1,5 +1,15 @@
 # Xous Startup Sequence
 
+The loader broadly runs in two phases, called phase 1 and phase 2:
+
+1. Allocate memory and copy stuff into RAM. This is where the tags are copied, and executable data is unpacked into memory. This is almost entirely a copying phase.
+2. Allocate and configure pagetables. This more or less does a second pass over the args table (so there's a possible TOCTOU here).
+
+After this it jumps to PID1.
+
+------------
+Below is historical notes
+
 This document describes how a running system is established.  It is, broadly,
 divided into four stages: