The most important chip in commodore 64 computer is the PLA chip. When this chip is broken, nothing will work and most certainly you will get a black screen after you try to turn it on. The original replacement chip is hard to get and if you find one it is not cheap. Luckily there are alternatives for replacement. It is possible to create one using EPROM, however the results of it's performance vary, or you can buy one on the market like SuperPLA, realPLA, U17 PLAnkton or PLAtinum.
FPGA's and CPLD's are certainly very cool devices. It is possible to create you own logical circuits and emulate real hardware chips on the lowest level. For this test project we will use Alera CPLD which is also known as MAX3000A and it's full code is ALTERA EPM3064ATC44-10. It has a programming capacity of 64 macrocells. A macrocell is the smallest programmable part inside a CPLD. The capacity of 64 is not very large compared for example to Altera Cyclone IV EP4CE6E22C8N FPGA chip which has 6272 logical elements, but it will be suitable for small projects.