Several varieties of custom integrated circuits are used within NES cartridges to expand system capabilities; most are difficult to replicate except by scavenging old cartridges.
The hardware lockout mechanism of the NES further complicates construction of usable physical cartridges.
NGDev Team who have released "Fast Striker and "Gunlord found a workaround with this.
Homebrew efforts for the Mega Drive/Genesis have grown, as there are now several full games scheduled for release in physical form, such as Rick Dangerous 1 & 2 and a port of Teenage Queen.
Pier Solar and the Great Architects and Frog Feast for the Mega Drive/Genesis and Mighty Mighty Missile for the Sega Mega-CD are examples of homebrew games already released for Sega consoles.
Neo-Geo AES and MVS cartridges have two separate boards: one for video, and one for sound.
If programming a cartridge for the system were to occur, it would involve replacing the old rom chips with your newly programmed ones as the cartridges are in a sense, Arcade boards.
For each scan line, the system's Television Interface Adapter can only draw two custom, eight-bit graphical objects, a twenty-bit "playfield", and three solid pixels: two "missiles" and one "ball". If a program takes too long to update the registers, the television will update the screen before the graphics are properly initialized, resulting in glitches or other video problems.
In this respect, Atari 2600 programming could be considered a form of hard real-time computing.
A QBASIC-like high level compiler named basiegaxorz exists for the Sega Genesis.
The Neo-Geo Home Cart and Arcade Systems can be tough candidates for homebrew development.
This is mostly the case because software production requires more resources, accurate emulators do not exist yet, and the consoles themselves often employ rather complex systems to prevent the execution of unauthorized code.
Homebrew developers must often exploit loopholes to enable their software to run.
Efforts have been made to use actual console hardware for many older systems, though.