# Frequently Asked Questions

## General

### What is ReviveSparc?

ReviveSparc is a clean-room reimplementation of the OpenSPARC ISA (instruction set architecture). It aims to provide a fully open-source, legally unencumbered implementation of the SPARC V9 architecture that can run operating systems and software.

### Is this affiliated with Oracle?

No. ReviveSparc is an independent open-source project. OpenSPARC and SPARC are trademarks of Oracle Corporation. We are not affiliated with or endorsed by Oracle.

### Why SPARC? Isn't it dead?

SPARC is still used in mission-critical systems, particularly in aerospace, defense, and high-reliability computing. The Fujitsu SPARC64 processors power Japan's Fugaku supercomputer. The architecture is elegant and well-documented, making it ideal for educational use. ReviveSparc aims to preserve the architecture for future generations.

## Technical

### What is the "clean room" process?

Developers implementing ReviveSparc have **no access** to the original OpenSPARC source code. We work exclusively from publicly available specification documents:
- SPARC Architecture Manual Version 9
- UltraSPARC T1/T2 Supplements
- VIS Instruction Set Manual

This ensures the code is entirely original and free from any AT&T licensing concerns that affected the original OpenSPARC codebase.

### What operating systems can run?

- **Linux** (6.x series, full support)
- **NetBSD** (10.x, full support)
- **OpenBSD** (7.x, in progress)
- **Bare-metal programs** (any ELF binary for SPARC V9)

### How fast is the emulator?

On a modern x86_64 system:
- Single-core, JIT disabled: ~50 MIPS
- Single-core, JIT enabled: ~200 MIPS
- 8-core, JIT enabled: ~800 MIPS aggregate

Performance is sufficient to boot Linux in a few seconds.

### Can I synthesize the RTL on an FPGA?

Yes. The Verilog RTL has been tested on:
- Xilinx Virtex-7 (XC7VX485T) — 4 cores at 50 MHz
- Xilinx Kintex-7 (XC7K325T) — 2 cores at 75 MHz
- Intel Arria 10 — 4 cores at 100 MHz

See the [RTL Synthesis Guide](rtl-synthesis.md) for details.

## Project

### How can I contribute?

The source repository and issue tracker are hosted on our Git instance at [git.revivesparc.com/Revivesparc/revivesparc](https://git.revivesparc.com/Revivesparc/revivesparc). See the [Community page](../community.html) for details. We welcome code contributions, documentation, testing, and hardware verification.

### What license is used?

BSD 2-Clause License. This permits both open-source and proprietary use, with minimal restrictions.

### Does ReviveSparc include any AT&T code?

No. ReviveSparc is a complete from-scratch reimplementation. Every line of code is original and written solely from the architecture specification.

### Are there plans for SPARC V8 (32-bit) support?

The emulator includes a SPARC V8 compatibility mode that handles 32-bit code. Pure 32-bit SPARC V8 is not a primary target, but the majority of V8 instructions are supported through the V9 backward compatibility features.

### Can I run Solaris?

Solaris 10 and Solaris 11 for SPARC are not currently supported. The primary targets are open-source operating systems. If you'd like to contribute Solaris support, please reach out on the mailing list.

### Why not just use QEMU's SPARC target?

QEMU's SPARC target is excellent for running SPARC binaries, but it is a functional emulator with less emphasis on:
- Cycle-accurate pipeline modeling
- Hardware synthesis targets
- Educational clarity

ReviveSparc complements QEMU by providing a reference implementation suitable for hardware design and teaching.

## Build Issues

### `make` fails with "undefined reference"

Ensure you have all dependencies installed. See the [Build Guide](build-guide.md) for your platform.

### The emulator crashes on startup

Run with debug output enabled:

```bash
./sparc-emu -d -v kernel.bin
```

This will show detailed trace information. File a bug report on the [issue tracker](https://git.revivesparc.com/Revivesparc/revivesparc/issues) with the output.

### Linux kernel hangs during boot

Common causes:
- Missing or incorrect device tree blob (use the DTB from `revivesparc.dtb`)
- Incorrect kernel command-line parameters
- Kernel built without ReviveSparc platform support

Try booting with `-append "earlyprintk debug"` to see kernel messages.