How faithful it is

JNEXT is built from the official ZX Spectrum Next FPGA sources — the VHDL that describes the actual hardware. Where a machine's behaviour is ambiguous or undocumented, the answer is taken from that source rather than guessed at, and pinned there by a test. In practice this means the emulator's answer is the silicon's answer.

Two honest caveats:

• Extreme cycle-exactness is not a goal. "Good enough to develop games on" is. A handful of demos that depend on sub-scanline timing may not be pixel-perfect.
• JNEXT 1.0 is not finished. Fixes are still pending and many features are on the roadmap. It works well enough for its author, and hopefully for you; the 1.0 release is meant to bring more users and more bug reports. Rough edges are listed rather than hidden — see chapter 8, Known issues — and bugs go to the issue tracker, https://github.com/jorgegv/jnext/issues.