Nintendo NES-001 User Guide - Page 7

This only applies to games which were originally made for the NES itself. Many developers have produced games since which have been released freely on the Internet. Downloading these is acceptable. As for original NES games, using them will remain illegal until either the developers grant permission for their use or the copyright expires, which is 75 years after they were made. Nintendo are very much against emulation. The company acted against the developers of UltraHLE [24], an emulator for their Nintendo 64 console, which they claimed violated copyright. Nintendo's objection was understandable as the console was still in use when UltraHLE was released. The presence of Nintendo 64 emulators represented a threat to Nintendo's income however, many believe that the law should make an exception for systems which are no longer in production and from which Nintendo no longer make any money. Despite emulation's ability to keep old games alive Nintendo refuse to release the copyright on old games so their use remains illegal. For more information on the legal issues of emulation, the reader is directed to Nintendo's own FAQ on the subject [25]. This is highly biased and ignores the legal uses of emulation. For a detailed response and clarification on this, the reader should look at [26]. 1.5 NES Hardware Overview Hiroshi Yamauchi's instructions to design a console which would be cheaper than the competition resulted in Nintendo deciding to use an outdated Central Processing Unit (CPU). Although a 16-bit processor would have coped with ease, to keep the price low they decided to use a variant of the 8-bit 6502 processor, developed by MOS technology in 1975. The chip would be sufficient to run the programs but would be unable to generate the graphics required so the company decided to use a second chip as a dedicated Picture Processing Unit (PPU), responsible for calculating and displaying the graphics. Figure 1-4 shows the top of the motherboard with the CPU and PPU indicated. PPU CPU Figure 1-4. The NES motherboard [27]. Nintendo designed the basic features required from the chips but found it difficult to find a company willing to produce such highly customised chips for the low price they were looking for. Ricoh agreed to manufacture the chips after Nintendo guaranteed them a three-million chip order. By the end of 1986 Nintendo was Ricoh's largest customer, accounting for between 60 and 70 percent of the company's semiconductor sales [10]. The functionality of the CPU is discussed in Part 2, that of the PPU is discussed in Part 3. Both chips feature their own internal memory, in the form of RAM. Games were usually stored on ROM chips within the game cartridges, which could be accessed by the CPU when the cartridges where inserted into the system. The hardware used for games is discussed in Part 4. The NES used memory mapped I/O to allow the processor to communicate with the other components, the PPU and the input devices. Memory mapped I/O is a technique where data 7