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Homebrew NES Cartridge

Cheaply add new games to your beloved old system
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For years, retrogamers have wanted new games for their old unsupported systems, especially the venerable 8-bit Nintendo.

Hardcore hackers have approached the problem by creating new games, or rediscovering lesser-known ones. People usually play these on an emulator, but it just isn't the same.

For the most hardcore, there is the option of creating a new cartridge using an old one as a "parts donor". Also there are expensive (usually in excess of 100 USD) flashcarts.

I envision a cartridge every homebrew hacker would soon be able to afford. The solution is to use a simpler and thus cheaper design.

Typically, a NES cartridge consists of a circuit board with contacts on one end, housed in a plastic casing. Mounted on the circuit board are various components, connected to the contacts. Usually these consist of 2 ROM chips, one for the program code, one for other data, a mapper chip, which performs memory paging, and the 10NES chip, which acts as the key to the (identical, but in lock mode) 10NES chip within the console. Some cartridges contain extra RAM and/or other chips that enhance the capabilities of the console.

The first problem we have is the 10NES lockout chip. There needs to be one in the cartridge or the console will not accept it. Hackers usually work around this by either using a "donor" 10NES chip from a original cartridge, or by disabling the 10NES chip in their console. Pirate company Color Dreams worked around the 10NES by temporarily knocking it out with a power surge. Tengen's solution was to create their own copy of the 10NES chip after reverse-engineering the original. Later, they integrated their "rabbit chip" as it was called, into the mapper chip.

Many people don't want to mod their NES, so we shouldn't have to disable the chip. Color Dreams' method doesn't work on all consoles, and is unreliable even on consoles it is known to work on. In this day and age, we have cheap, reprogrammable, general-purpose microcontrollers, so I think Tengen's method is the way to go. Much about the function of the 10NES chip is known, so recreating it should be relatively easy. Also, I don't like the idea of having to destroy an old cartridge to make a new one, because no matter what game it is, it's a piece of history. Since we will need a mapper chip anyway and any general-purpose chip that can be a mapper chip is overkill for a 10NES chip, one chip should be all we need for this.

So now we need the program and data storage, which is accessed by console through the mapper. Usually there are two EEPROM chips for this purpose. With a special mapper chip, however, only one large chip is needed. A single NAND flash chip would be used for this, because these chips are convenient and are now cheap.

But where would the mapper/10NES chip's firmware reside, you ask? Some general-purpose microcontrollers nowadays have their own flash memory and RAM integrated. But if we wanted to use a cheaper chip, an area on the NAND chip could be reserved instead. Since NANDs are rewriteable, an area could also be reserved for game saves (SRAM). No battery-backing would be necessary.

Some I/O pins on the mapper/10NES chip could be freed if shift register chips are used. This could allow for a cheaper chip, or for the chip to also serve other purposes, for example it could act as a DSP or co-processor to allow for more advanced games. More importantly, USB upload connectivity could be added.

Casing is the easiest part. Homebrew plastic case-making has been pioneered by folks such as Ben Heck, and is now a skill known by many. The simplest method would probably be to paint and label some plexiglass, and glue/screw together.

This is just the basic model. Other features such as additional RAM (which some games require), multicart functionality (this should be possible just by using a larger flash chip and a different mapper/10NES firmware design), or an extra microcontroller for more advanced games, could be added if desired. Perhaps even debugging features could be added. Somebody enterprising enough could make good money by selling these.

Spacecoyote, Aug 17 2008

Cuttle Cart http://schells.com/cuttlecart.shtml
The Cuttle Cart for the Atari 2600 [JakePatterson, Aug 17 2008]

Starpath Supercharger http://en.wikipedia...arpath_Supercharger
The Starpath Supercharger for the Atari 2600 [JakePatterson, Aug 17 2008]

NES10 chip reverse-engineered http://hackaday.com...-security-in-depth/
[Spacecoyote, Jan 20 2010]

NES ROM cartridge NES_20ROM_20cartridge
Half-baked. [Aq_Bi, Jan 20 2010]

[link]






       I've seen a cable which plugs into a cartridge slot on some console or other, possibly the Megadrive/Genesis or maybe an Atari, which is then plugged into a PC so the console can then use data on the PC as if it's a ROM. I can't remember any more details. The problem with that is it still needs a PC to be powered up and so on to work. [+].
nineteenthly, Aug 17 2008
  

       I have a modern cartridge for the Atari 2600 that has a cable with a phono plug. Software can be assembled and then the binary converted into an audio format that is understood by the cartridge. The cartridge also has some additional RAM that your software can utilize. The reason for the audio interface is that there was similar product in the early eighties that did basically the same thing, except the intention was not for home- brew games but rather the line of games that the company released on audio cassette. The modern device is called the Cuttle Cart, and the classic one is the Starpath Supercharger. I'll try to find some links. (update... links added)
JakePatterson, Aug 17 2008
  

       Yeah, I know this has been done for other consoles but not so much for the NES, because the NES is more picky.
Spacecoyote, Aug 17 2008
  

       Every time I look at this, I see "Hebrew....". I have no idea why.
MaxwellBuchanan, Jan 20 2010
  

       Maybe it plugs in from right to left?
Wrongfellow, Jan 21 2010
  

       So what's the problem with an emulator? (they even have adapters for the old NES controllers) Last I checked you could download every single Nintendo licensed cartridge. Since this is exactly what you would use in the dummy cartridge why not skip the intervening hardware and play on your PC?
WcW, Jan 21 2010
  

       dude get the original cartridge then. This is like a record player with the needle hooked to a cd player headphone.
WcW, Jan 21 2010
  
      
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