ANDESITE

A ZX Spectrum Next emulator, written for the Next itself rather than for the machines it can pretend to be. Its time base is the 28 MHz master clock, not T-states: the CPU runs at 3.5, 7, 14 or 28 MHz against a video chip fixed at a 14 MHz dot clock, so the two share no unit and every device is counted in the clock they all actually share.

The picture is built the way the hardware builds it. The frame buffer is 640x256 dot clocks rather than pixels, because the machine resolves two things per standard pixel. Timex Hi-Res is 512 across the width the other modes fill with 256, and Layer 2 has a 640x256 mode, so nothing has to be approximated to fit. Layer 2 in all three modes, the ULA with every Timex mode and ULANext, LoRes, the tilemap and 128 hardware sprites are composited by layer order, per-entry priority and both blend modes, and the Copper runs inside that same walk so a register write lands on the dot it was written for.

Storage is an SD card as a sparse disk image, with esxDOS emulated at the RST $08 trap over the same FAT volume, so a game reads and writes its own files, high scores and saved progress included. Sound is the beeper, three AY-3-8912s through Turbo Sound Next and the four 8-bit DACs, mixed in stereo through a band-limited buffer at the master clock. Sprites, the tilemap, the Copper, the ZXN DMA, the Z80 CTC, the Kempston mouse, the DS1307 clock and save states each have their own test suite.

Available on Windows, Linux, macOS, Android, iOS, and WebAssembly. Andesite is plain, portable C11 with no exotic dependencies, so a port to video game consoles is well within reach. Contact us if that is of interest.

Retro City Skyline

Andesite in Action

Commercial games running unmodified on Andesite, shown to demonstrate compatibility.

Black & White running on Andesite
Black & White © Pat Morita Team
Bonsai Next running on Andesite
Bonsai Next © JuanGM
Delta's Shadow running on Andesite
Delta's Shadow © Sinc LAIR
The Lost Temples running on Andesite
The Lost Temples © Pat Morita Team

Andesite Options

Third-Party Software