1.1 --- a/Electron.txt Wed Apr 12 16:09:28 2017 +0200
1.2 +++ b/Electron.txt Fri Feb 22 16:05:35 2019 +0100
1.3 @@ -83,7 +83,10 @@
1.4 disabling the video signal, effectively achieving the same as blanking the
1.5 palette, would be a very simple but useful enhancement that would speed up
1.6 programs needing to render large amounts of non-real-time content to the
1.7 -screen.
1.8 +screen. This would also have been beneficial for display expansions connected
1.9 +to the main expansion bus, along the lines of the Jafa MODE 7 adapter, where a
1.10 +peripheral would maintain its own framebuffer by registering writes on the bus
1.11 +to the display memory region.
1.12
1.13 Improving Display Capabilities
1.14 ------------------------------
1.15 @@ -110,6 +113,24 @@
1.16 low-memory screen mode usage - in order to retain as much content in memory as
1.17 possible - would also be diminished.
1.18
1.19 +Simplifying the ULA
1.20 +-------------------
1.21 +
1.22 +An apparent motivation in the design of the Electron was to reduce the chip
1.23 +count. However, this then requires that the ULA perform a range of different
1.24 +roles. Some roles, such as handling cassette input and output, might have been
1.25 +natural for the ULA given Acorn's previous designs, but others, such as
1.26 +generating sound, arguably demand the integration of a lot of additional
1.27 +functionality unless the capabilities are significantly reduced. Obviously, in
1.28 +the Electron, the sound capabilities were reduced to a point where they were
1.29 +considered a weakness of the machine.
1.30 +
1.31 +The design of the Commodore Plus/4 also sought to increase integration -
1.32 +combining the sound and video chips in that case - but this was arguably more
1.33 +feasible given the fabrication technology available within Commodore.
1.34 +Meanwhile, Acorn might have been better off retaining a separate sound chip
1.35 +and designing the ULA to interface with it instead.
1.36 +
1.37 About this Document
1.38 -------------------
1.39