Application-Specific Integrated Circuit (ASIC)
An ASIC is an especially manufactured custom Chip chip designed to fulfill fulfil special fonctionsfunctions.
The main reason is to perform special tasks or combine different electronic componnents components into a single Integrated Circuit (Chipchip).
==Amstrad Custom chips==
The Amstrad CPC used one custom chip : the video [[Gate Array]] (also called VGA...but nothing to share – no connection with the Video PC standard)...)
Latter [[CPC]] cost down series included a "pre-ASIC" to merge the VGA and the CRTC.
The Amstrad [[Plus]] include included a "second heart" simply referred as the ASIC.
CPC+ ASIC's part number is 40489
This Amstrad Plus ASIC perform many additionnal additional features that the old CPC series couldn't : the "Plus Features".
*Hardware Sprites.
*[[CRTC]] emulation.
*Hardware ScrollingsScrolling.*Maybe some interactions with the [[Amstrad Cartridge Identification Device|ACID]] chip in Cartridgescartridges.
*DMA sound channels.
*Many many more.
== Known Flaws==
The Asmtrad Amstrad Plus ASIC improve improved a lot of the old CPC 's capability.
Yet this was a bit flawed.
*Despite removing some tasks from the CPU ([[Z80]]), the ASIC had to use specific central memory addresses, so "took away" this memory from the CPU...
Not This was not that important for a 64Ko Ram 64KB RAM system (464+ and GX4000) yet this is a serious limitation when dealing with Extra memory (6128+ and Extra Ram RAM peripheral)
*There's a DMA bug (Help needed).
*Some argue that the Asic ASIC simply badly Emulates emulates an old CPC, but it is not really one. The Colours colours are slightly different and some softwares software (games) couldn't work until modified (Addons patches for such Old old CPC games often exist now).
As a result, some people say that the Plus is not a CPC...
*[http://en.wikipedia.org/wiki/Application-specific_integrated_circuit ASIC at Wikipedia]
General informations information on ASICs.
*[http://www.kjthacker.f2s.com/docs/arn5new.html Asic and Plus features at Unofficial CPC ressources 1.4]
*[http://www.kjthacker.f2s.com/docs/arnold5a.html Asic and Plus features at Unofficial CPC ressources 1.5]
*[http://www.kjthacker.f2s.com/docs/cpcplus.html Extra Plus Hardware InformationsInformation]
[[Category:CPC Plus]][[Category:Hardware]][[Category:Programming]][[Category:Datasheet]][[Category:Graphic]]
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