This projects original intention was to make an updated version of Bodo Wenzels ZX97 ZX81 clone. This has been done, but not according to the original plan which was to use a real Z80, separate memory chips and the ZX97 ULA replacement. Instead the entire ZX81 was implemented in one FPGA! Since then three more systems have also been implemented.
If you also would like to build your own Arcade Games you should have a look at FPGA Arcade.
What you need to get started:
If you want to know what all this FPGA and VHDL mean, Keith Howell has an introduction.
Important legal notice!
While the VHDL source code written for this project is in the public domain, this is not the case with the T80 soft core and the included ROM files. T80 is released under the BSD license and the ROMs have different restrictions. The only ROM with a clear statement from it's owner is the ZX Spectrum ROM, here is what Amstrad has to say. In other words: Don't distribute this ROM with hardware! The ZX81 ROM is owned by Nine Tiles Networks, and as far as we know they do not oppose distribution of this ROM, even with hardware, but we take no responsibility for what happens if you do. The Jupiter ACE ROM has no known copyright holder. The TRS80 ROMs are not in included, since as far as we know, this is not allowed. If you know any of this to be incorrect, let us know this!
There is a discussion group at http://groups.yahoo.com/group/zxgate but it will probably migrate to