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NixVM

A 32-bit virtual CPU and memory controller built for easy system integration and expansion. Designed for creating "Fantasy console"s but could easily be used as the back end of a scripting language.

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README

NixVM — Virtual Microprocessor & Fantasy Console Engine

Copyright (c) 2026 Nicholas Smith
Licensed under the GNU General Public License v3.0

📖 Overview

NixVM is a modular, high-performance 32-bit virtual RISC microprocessor, memory architecture, and toolchain designed as a universal foundation for building fantasy consoles, retro computers, and embedded scripting runtimes.

Instead of reinventing custom instruction sets and memory controllers for every new virtual console, NixVM provides an extensible, dependency-free core engine with first-class tooling: A Pascal compiler, an Intermediate Representation (IR) linker, a full text assembler, a reverse-engineering disassembler, a universal cartridge packaging system (.nvm), and a vm harness system for creating stand alone executable (.exe) files.

⚡ Key Architectural Features

  • 32-Bit Register Architecture: 16 general-purpose 32-bit registers (R0–R15), condition code setters (sete..setge), bit manipulation (bset, bclr, btst), and dedicated hardware frame pointers (BP, SP).
  • Auto-Prefetching Immediate Pipeline: Transparent immediate operand decoding via hardware pseudo-register R13 (Imm) providing clean, branchless ALU operations with zero opcode duplication.
  • Integrated 32-Bit FPU: Hardware IEEE-754 Single-precision floating-point unit (fadd, fsub, fmul, fdiv, fsin, fcos, ftan, fsqrt, fln, fexp).
  • Sandboxed Memory Model: Power-of-two virtual memory addressing with zero-overhead wrapping and memory bounds protection.
  • High-Level System Services: Built-in dynamic heap management, managed string operations with $O(1)$ length lookups, formatted I/O (DebugPrint, StringFormat), and programmable hardware timers.
  • Cooperative Frame Engine: Throttled host execution with cooperative yielding (yield), real-time delta timing (Delta), and hardware interrupt support.
  • Universal Cartridge Format (.nvm): Self-describing, binary-safe ROM cartridge format specifying target hardware requirements and memory budgets.

📚 Technical Documentation (WiP, often out of date)

Explore the complete, language-agnostic hardware specification manuals:

Specification Document Description
CPU & Instruction Set Reference Core processor architecture, register map, flags layout, ABI calling conventions, and complete datasheet for all 80+ instructions.
Memory & MMIO Reference Virtual memory map, Core System Area ($0000–$04DF), System Registers (Delta/Elapsed), hardware timers, and OEM peripheral mapping.
SysCalls & Interrupts Reference Complete SysCall ABI, heap/string services, hardware panic error codes, and the 16 prioritized interrupt vectors.
Assembler & Toolchain Guide Assembly syntax, directives (.embed, .include, .align, .res), label scoping (@local), constants (.equ), and CLI tool documentation.
ROM Cartridge Format (.nvm) The official 92-byte NVMX cartridge header specification, loading protocol, and hardware layout integrity checks.

📜 License

NixVM is open-source software licensed under the GNU General Public License v3.0. See the LICENSE file for more details.