From GameBrew

AuthorIan Cowburn
Last Updated2008/12/30

DS81 is a Sinclair ZX81 emulator.


  • Most things expected from an emulator.


Note: In order to use this emulator, you will need to obtain the program image files (in .d formats).

Download and extract ds81.nds to the apps folder of card.

Create a folder called ZX81SNAP in the root of flash card for legally owned files (in .d formats).

Run DS81 from card's apps menu.

User guide

Instruction can be found here.

A few games are included to try out:

  • ZX81 ROM © 1981 Nine Tiles Networks Ltd.
  • Mazogs © 1981 Don Priestley.
  • City Patrol © 1982 Don Priestley.
  • Sabotage © 1982 Don Priestley.
  • 3D Monster Maze © 1983 Malcolm E. Evans.


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  • Added memory snapshots.
  • Added auto-load of AUTO snapshot.
  • Added save/load of keyboard mappings.
  • Added ability to SAVE from BASIC.
  • Increased maximum number of files to 1024 in selector.
  • Forty Niner still goes mental, so there's still an emulation bug somewhere.


  • Made file selector filter case-insensitive.


  • Controlled version of keyboard fix.
  • Added seperate ARM7/ARM9 code so able to use Wifi and its web server as a file store. Wifi lib doesn't work with access point during development, so reverted to a simpler ARM9 build. Which has made a merry mess of the CVS repository.
  • Compiled with newer version of libfat so that the DLDI interfaces can be used (thanks Chism). At last it loads ZX81 programs into the emulator. Moved to R20 of the toolchain and the new libnds.
  • Added support for text mode underlayed with a rotation screen for bitmap purposes.
  • Added code to ZX81 emulation to notice changes to register and search for hires display files. Works for a lot of hires games, though needs proper display emulation for Manic Miner, so that won't work
  • Improved speed of hi-res code.
  • Fixed attempted load in ZX81SNAP - the FAT libs seem to want UNIX style directory seperators.
  • Added file selector with LOAD "* "
  • Handling of 1K display files is a bit better.
  • Added option for RAM in place of ROM mirror.
  • Changed lower screen to 8-bit deep to allow overlay a tiled mode.
  • Added lower screen console routines.
  • Added Machine Code Monitor.

V1.1a uncontrolled release

  • Fixed hideous mess up that was the keyboard fix.


  • Added external FAT file loading.
  • Added Mazogs as a built-in tape (code courtesy of Paul Fearnley).
  • Fixed bug where the ROM input routine could be easily locked up. This was caused by a problem in the way the LASTK system variables was set up from the house-keeping routine.

External links