ZX81¶

Overview¶

Sinclair’s ZX81 (1981) delivered a low-cost home computer that relied on overlays and multi-purpose keybindings. REG-Linux points the zx81 group at the libretro: 81 core so the keyboard-first experience can be remapped to controllers when needed.

Technical specifications¶

CPU: Zilog Z80 running at 3.25 MHz with minimal supporting logic to keep costs down.
Memory: 1 KB of RAM on-board, expandable via external RAM packs to 16 KB or more.
Display: Monochrome 64×48 character display overlaid on a 256×192 video matrix with software-timed raster refresh.
Sound: Single-bit beeper toggled by the processor for simple tones or tape motor control.

Quick reference¶

ROM folder: /userdata/roms/zx81
Accepted formats: .tzx, .p, .zip, .7z
Emulators: libretro: 81
System group: zx81

BIOS¶

No BIOS dump is required for the ZX81 core.

ROMs¶

Copy cassette snapshots or program files into /userdata/roms/zx81. The core reads .tzx and .p images directly, and zipped archives are supported if the .tzx file resides at the root of the archive.

Emulators¶

libretro: 81¶

RetroArch exposes the usual zx81.* options (videomode, shaders, pixel_perfect, etc.). Use the Quick Menu ([HOTKEY] + south ) to tweak the display and the input device type. X-Keys also toggle features like global.81_chroma_81 for colorization and global.81_highres for the WRX high-resolution mode.

Controls¶

RetroArch maps the cursor joystick type to the D-pad and uses South/East/West to emulate the keyboard fire button. If you want controller support, open the Quick Menu, go to Input > Input User 1 Binds, and set User 1 Device Type to Cursor Joystick.

Troubleshooting¶

When the emulator keeps focusing the on-screen keyboard, set user 3’s device to “Sinclair Keyboard” and leave users 1–2 on joysticks for gameplay.
If a zipped snapshot refuses to load, extract it and place the .tzx file beside the archive so the core can find the proper header.
For broader RetroArch tips, visit the generic support pages.