Changes
Added picture of the decapped ACID chip
[[Image:Inside GX4000 cart 1.jpg|frame|right|ACID protection chip within a cartridge (bottom)]]
The '''ACID''' (Amstrad Cartridge Identification Device) protection chip is used in the [[GX4000 cartridge|cartridges]] of the [[Plus]] series and the [[GX4000]] game console. After Nocash decrypted the internal algorithms it is possible to replace the protection chip with a complex programmable logic device (CPLD).
<gallery>
Image::ACID Init by Grim.png|Init/RESET, CLK, CCLR, SIN (init sequence)Image:ACID-SIN.jpg|CLK and SINImage:ACID-CCLR.png|CLK and CCLR(and some offtopic signals) (from CPC, without ACID connected)
</gallery>
Note: The two GND pins are interconnected with each other (inside of the chip). The NC pin seems to be always high.
== Clones ==
* An ACID replacement using a Xilinx XC9536 CPLD and some [[Verilog implementation of the ACID chip|Verilog code]] based on nocash's reverse engineering work has been built by [[Octoate]] and [[Nilquader]].
* Miguel Angel (aka mcleod_ideafix) has published all the info about his implementation of the ACID in a CPLD, verilog sources included [http://www.zxprojects.com/index.php/analisis-del-chip-acid/62-analisis-del-chip-acid-del-amstrad-cpcgx4000]
* It's possible to use the CPC+ without ACID by exploiting a timing bug in the CPC+/GX4000-ASIC Chip. (Developed by [[Nilquader]])
<gallery caption="Running CPC+ without ACID">
Image:NoAcid.jpg|GX4000 running without ACID
Image:NoAcid_sch.png|Schematics
</gallery>
== Pictures ==
* ACID chip decapped. Many thanks to Sean Riddle!
<gallery>
Image:40908_Metal_Small.jpg
</gallery>
== Misc ==
[[Category:Hardware]][[Category:Cartridges| ]][[Category:CPC Plus]][[Category:CPC Internal Components]][[Category:Amstrad Products]][[Category:Electronic Component]]
