# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1441662228 -7200
# Node ID 752c60951649676cda506b1ca3cbea387c09336a
# Parent  cabf7421f46120be39509dffef62cf2e81deca43
Added a note about the 2MHz RAM access enhancement.

diff -r cabf7421f461 -r 752c60951649 Electron.txt
--- a/Electron.txt	Sun Sep 06 13:41:27 2015 +0200
+++ b/Electron.txt	Mon Sep 07 23:43:48 2015 +0200
@@ -36,6 +36,17 @@
 Improving System Performance
 ----------------------------
 
+The ULA and the CPU share access to the RAM, meaning that when the ULA needs
+to fill the display, the CPU will either take it in turns with the ULA to
+access RAM or even relinquish access to the RAM for the entire duration of the
+visible portion of a display line. However, even outside these periods of
+contention, it appears that the CPU still only accesses the RAM at 1MHz, even
+though the RAM can sustain 2MHz access (and indeed does when both the CPU and
+ULA access it in turns). By allowing the CPU to entirely take over the RAM
+outside display periods (just as the ULA can do) and to access it on every
+2MHz cycle, performance would be significantly improved: the CPU would be able
+to do twice as much work in the largest-memory screen modes, for example.
+
 Although RAM is accessed by the CPU at 1MHz, ROM is accessed at 2MHz. Thus,
 deploying software that runs from ROM can potentially provide significant
 performance benefits. Since the unexpanded Electron provides no convenient