# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1684245260 -7200
# Node ID ab28336894bcdf1f8f1c9173dd8f61d72a7213d5
# Parent  e16067046f2af3a9d19182220e61d6f2fd1ab46f
Added a suggested text mode approach.

diff -r e16067046f2a -r ab28336894bc ULA.txt
--- a/ULA.txt	Mon Oct 17 01:09:49 2022 +0200
+++ b/ULA.txt	Tue May 16 15:54:20 2023 +0200
@@ -1554,6 +1554,31 @@
 MODE 7 support could be made available, potentially as a hardware option
 separate from the ULA.
 
+Enhancement: 40-Column Text Modes by Interleaving Screen and Bitmap Accesses
+----------------------------------------------------------------------------
+
+Suggested here: https://stardot.org.uk/forums/viewtopic.php?p=393243#p393243
+
+The ULA could be run in high-bandwidth mode to fetch character codes from
+screen memory in one cycle and then to use the character code to look up a
+pixel row of a character bitmap, reading that bitmap slice in the following
+cycle. The bitmap would be converted to pixel values that would then be
+emitted over the subsequent two cycles concurrently with the preparation of
+the next character's pixels.
+
+  2MHz cycle: 0 1 2 3 4 5 ...
+  Reads:      C B C B C B ...
+  Pixels:         a   b   ...
+
+The memory access to bitmap data would be computed as follows, assuming the
+normal eight pixel height and single-byte encoding of character bitmaps:
+
+  bitmap address = bitmap table base + (character code * 8) + bitmap row
+
+Each successive pixel row on the screen would expose the appropriate row in
+the character bitmap, with this "bitmap row" looping from 0 to 7 repeatedly.
+Spacing between character lines could be introduced as already done in MODE 6.
+
 Enhancement: Compressed Character Data
 --------------------------------------