# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1392511362 -3600
# Node ID b9641b6b8b16a279e63cb4d52e88a9a59a89b4cd
# Parent  6363b9a428654043a5936362bb0d9d685c1aca83
Added notes about cartridges, Econet, and region filling.

diff -r 6363b9a42865 -r b9641b6b8b16 Electron.txt
--- a/Electron.txt	Sat Feb 01 17:55:57 2014 +0100
+++ b/Electron.txt	Sun Feb 16 01:42:42 2014 +0100
@@ -42,11 +42,18 @@
 means of installing ROM-based software - the Plus 1 and other expansion units
 offered ROM cartridge slots, and various expansions provided ROM sockets - the
 improved Electron would ideally need to offer a ROM cartridge slot as part of
-the unexpanded machine. A side-benefit of adding this feature to the base
-machine would arguably be an increased demand for cartridge-based software,
-potentially at a slightly higher price and also offering additional hardware
-features if necessary, thus making any cost incurred in the manufacture of the
-base unit more bearable.
+the unexpanded machine.
+
+A side-benefit of adding this feature to the base machine would arguably be an
+increased demand for cartridge-based software, potentially at a slightly
+higher price and also offering additional hardware features if necessary, thus
+making any cost incurred in the manufacture of the base unit more bearable.
+And in school environments where unexpanded BBC Microcomputers were often used
+with tapes, the use of ROM cartridges for instant and reliable loading of
+software would have given the Electron a practical advantage: it would be a
+cheaper machine that could later be expanded with disk drives (the other main
+way of providing fast and reliable storage) while still offering a substantial
+saving over the BBC Micro.
 
 The Slogger/Elektuur turbo board modified the system to permit the CPU to
 access the bottom 8K of RAM without interruption by the ULA. This feature,
@@ -76,3 +83,16 @@
 circuitry and would only benefit UHF and colour composite video displays, but
 the latter limitation might not be a significant issue for the majority of the
 intended audience.
+
+Supporting Local Area Networking
+--------------------------------
+
+The Electron was mostly aimed at the home market, but a cheaper computer would
+have been very attractive for schools, especially those wanting to purchase a
+number of machines for networking. Having an option available in the standard
+Electron would have given such customers a cheap Econet terminal, albeit
+without the MODE 7 capabilities of the BBC, whilst ignoring the requirement of
+reliable, fast storage that standalone machines need to have in such
+environments. With content available on demand over the network, the need for
+low-memory screen mode usage - in order to retain as much content in memory as
+possible - would also be diminished.
diff -r 6363b9a42865 -r b9641b6b8b16 ULA.txt
--- a/ULA.txt	Sat Feb 01 17:55:57 2014 +0100
+++ b/ULA.txt	Sun Feb 16 01:42:42 2014 +0100
@@ -529,6 +529,35 @@
 retain the details of such areas and additional logic to control the fill
 operation.
 
+Enhancement: Region Filling
+---------------------------
+
+An alternative to memory writing might involve indicating regions using
+additional registers or memory where the ULA fills regions of the screen with
+content instead of reading from memory. Unlike hardware sprites which should
+realistically provide varied content, region filling could employ single
+colours or patterns, and one advantage of doing so would be that the ULA need
+not access memory at all within a particular region.
+
+Regions would be defined on a row-by-row basis. Instead of reading memory and
+blitting a direct representation to the screen, the ULA would read region
+definitions containing a start column, region width and colour details. There
+might be a certain number of definitions allowed per row, or the ULA might
+just traverse an ordered list of such definitions with each one indicating the
+row, start column, region width and colour details. One could even compress
+this information further by requiring only the row, start column and colour
+details with each subsequent definition terminating the effect of the previous
+one. However, one would also need to consider the convenience of preparing
+such definitions and whether efficient access to definitions for a particular
+row might be desirable. It might also be desirable to avoid having to prepare
+definitions for "empty" areas of the screen.
+
+One application of region filling is that of simple 2D and 3D shape rendering.
+Although it is entirely possible to plot such shapes to the screen and have
+the ULA blit the memory contents to the screen, such operations consume
+bandwidth both in the initial plotting and in the final transfer to the
+screen. Region filling would reduce such bandwidth usage substantially.
+
 Enhancement: Hardware Sprites
 -----------------------------