page_title: List of Super NES enhancement chips
section_title: S-DD1
hierarchical_section_title: List of Super NES enhancement chips / S-DD1
caption_attribution_description: English: S-DD1(RF5C341) chip for SFC(SNES) in the game cartridge "Star Ocean".
context_page_description: The list of Super NES enhancement chips demonstrates the overall design plan for the Super Nintendo Entertainment System, whereby the console's hardware designers had made it easy to interface special coprocessor chips to the console. This standardized selection of chips was available to increase system performance and features for each game cartridge. As increasingly superior chips became available throughout the SNES's retail market years, this strategy originally provided a cheaper and more versatile way of maintaining the system's market lifespan when compared to Nintendo's option of having included a much more expensive CPU or a more obsolete stock chipset.
  As a result, various enhancement chips were integrated into the cartridges of select game titles. The presence of an enhancement chip is most often indicated by 16 additional pins on either side of the original pins, 8 to each side.
context_section_description: The S-DD1 chip is an ASIC decompressor made by Nintendo for use in some Super Nintendo Entertainment System Game Paks. Designed to handle data compressed by ABS Lossless Entropy Algorithm, a form of arithmetic coding developed by Ricoh, its use is necessary in games where massive amounts of sprite data are compressed with a total design limit of 32-megabits. This data is decompressed dynamically by the S-DD1 and given directly to the picture processing unit.
  The S-DD1 mediates between the Super NES's Ricoh 5A22 CPU and the game's ROM via two buses. However, the controlling 5A22 processor may still request normal, uncompressed data from the game's ROM even if the S-DD1 is already busy with a decompression operation. This form of parallelism allows sprite data to be decompressed while other types of data are quickly passed to the main CPU.
  Star Ocean and Street Fighter Alpha 2 are the only games that use this chip. Emulation of the S-DD1 initially proved to be difficult, requiring "graphics packs" to be provided for the affected titles, until the compression algorithm was identified.
caption: S-DD1 chip in Star Ocean
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