PowerPak

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The PowerPak is a flash cartridge made by RetroUSB. It uses an FPGA to emulate a wide variety of mappers, allowing the user to store a large collection of ROMs on a single Compact Flash card and run them on an NES. It is widely used by homebrew NES developers to test their software.

In addition to NES ROMs, the PowerPak is able to play FDS disk images, as well as NSF music files.

Famicom expansion audio is supported, and output on the EXP 6 expansion pin on the cartridge connector. A simple modification to the NES allows the expansion audio to be mixed with its output.

Specifications:

  • PRG size: 512 KB (252 KB for NSF)
  • CHR size: 512 KB

Product page: http://www.retrousb.com/product_info.php?products_id=34

Mapper Compatibility

The PowerPak mappers have undergone several revisions, gradually improving compatibility. After official development ceased in 2010, Loopy and TheFox have each created a supplemental set of PowerPak mappers to improve its capabilities.

Power Mappers

TheFox created a set of revised PowerPak mappers to supplement or augment the existing ones, most notably adding a savestate feature.

Download: http://kkfos.aspekt.fi/projects/nes/powerpak/powermappers/

Known problems:

  • Mapper 4 IRQ is has a reliability problem on some systems, causing shaky status bars and other similar problems.

Loopy's Mappers

Loopy released a set of revised PowerPak mappers in 2011, adding fixes and additional support for several mappers:

Download: https://home.comcast.net/~olimar/NES/powerpak_loopy.zip

Notes:

  • Mapper 3 now supports unlicensed oversize variants (e.g. used by Panesian games).
  • Mapper 4 now supports both Startropics and Low G Man.

Offical Mappers V1.34

The last official release of mappers was in 2010. It supports a wide variety of popular mappers.

Download: http://www.retrousb.com/product_info.php?products_id=34

Supported mappers:

Known problems:

  • Mapper 3 limited to CNROM support, excluding unlicensed oversize variants (e.g. used by Panesian games).
  • Mapper 4 does not support Startropics. (See mapper 4 and MMC6.)
  • Mapper 5 (MMC5) is incomplete, and fails to run most MMC5 games.
  • Mapper 23 (VRC2/4 variants) is listed as buggy.
  • Mapper 92 (Jaleco-JF variant) is listed as buggy.
  • Mapper 95 (Namcot-3425) is listed as buggy.
  • Mapper 96 (Oeka Kids) is listed as buggy.

Software development limitations

Aside from mapper incompatibility, there are minor differences between running NES programs on the PowerPak versus a traditional single-game cartridge.

  • The PowerPak does not accurately simulate power-on state. Because power-on always boots the PowerPak menu, RAM and various registers will be initialized to a consistent state before any NES ROM is chosen to run. (Reset state, howevere, is not affected by this problem.)
  • Open bus behavior may be different in several memory regions that are used by the PowerPak, but would not be connected on a regular cartridge.

PowerPak development resources

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