Kaspa FPGA mining guide

Kaspa’s kHeavyHash algorithm favors FPGAs for efficient, decentralized mining, with Kintex-7 boards offering optimal performance and power efficiency.

Jul 29, 2025 at 07:43 am

Understanding Kaspa and Its Unique Mining Algorithm

Kaspa is a high-speed, scalable blockchain that operates using a blockDAG (Directed Acyclic Graph) structure instead of a traditional linear blockchain. This design allows for faster transaction processing and improved network throughput. The consensus mechanism used by Kaspa is called GHOSTDAG, which enables parallel block processing while maintaining security and consistency. Because of its rapid block generation—every second—Kaspa requires efficient mining hardware to remain competitive.

Mining on the Kaspa network relies on the kHeavyHash algorithm, a memory-hard variant derived from HeavyHash, which itself is based on SHA-3. This algorithm is specifically designed to resist ASIC dominance and promote decentralization by being friendly to FPGA and GPU miners. However, FPGAs (Field-Programmable Gate Arrays) offer a significant advantage in power efficiency and performance flexibility compared to GPUs. Understanding kHeavyHash is essential because it dictates the type of hardware optimization required for efficient mining.

Selecting the Right FPGA Hardware for Kaspa Mining

Not all FPGAs are suitable for mining Kaspa. The key factors to consider include logic cell count, memory bandwidth, power consumption, and availability of open-source mining cores. Popular FPGA development boards used in the community include:

• Xilinx Kintex-7 KC705
• Alchitry Au (with Xilinx Spartan-7)
• Numato Mimas V2 (Spartan 6)
• Lattice MachXO3-based boards for lightweight testing

Among these, the Kintex-7 series is most widely adopted due to its balance of resources and community support. Ensure your FPGA board has sufficient Block RAM (BRAM) and DSP slices to handle the kHeavyHash computations efficiently. Also, verify that the board supports PCIe connectivity or can interface with a host PC via USB for control and data transfer.

Setting Up the FPGA Development Environment

Before deploying a mining core, you must configure your development environment. This involves installing FPGA design tools and obtaining the necessary mining firmware. Follow these steps:

• Install Xilinx Vivado HLx Design Edition (for Kintex-7 or Spartan-7 boards). This software suite is required to synthesize, implement, and program the FPGA.
• Download a compatible kHeavyHash mining core from trusted repositories such as GitHub. Look for projects labeled as “Kaspa FPGA miner” or “kHeavyHash FPGA implementation.”
• Clone the repository using Git:
  git clone https://github.com/[username]/kaspa-fpga-miner.git
• Open the project in Vivado and verify that the target device matches your FPGA board.
• Check synthesis constraints (XDC files) to ensure correct pin mapping for clock inputs, PCIe, or UART interfaces.

During implementation, pay close attention to timing closure. Failing to meet timing requirements will result in unstable or non-functional mining operation. Use Vivado’s timing analysis tools to identify critical paths and apply optimizations such as pipelining or clock domain separation.

Flashing and Deploying the Mining Core

Once the design passes synthesis and implementation, it’s time to generate the bitstream and program the FPGA. Use the following process:

• In Vivado, navigate to Generate Bitstream under the “Program and Debug” menu.
• Wait for the bitstream generation to complete. This may take several minutes depending on design complexity.
• Connect your FPGA board to the computer via USB or PCIe.
• Open Hardware Manager in Vivado and locate your connected device.
• Click Program Device and select the generated .bit file.
• Confirm successful programming by checking the board’s status LEDs or using a serial terminal to monitor boot messages.

After flashing, the FPGA will begin executing the mining core logic. It does not mine independently—it must communicate with a mining software client on the host machine to receive work and submit shares.

Configuring the Host Mining Software

The FPGA acts as a computation accelerator, but it requires coordination with a host-based miner to interface with the Kaspa network. The most commonly used software is kaspaminer, an open-source CPU/FPGA-compatible miner. Configuration steps include:

• Download the latest release of kaspaminer from the official GitHub repository.
• Compile it on your system (Linux is recommended):
  make
  
  Ensure dependencies like libcurl and OpenSSL are installed.
• Modify the configuration file (config.json) to specify the FPGA connection type (e.g., USB, PCIe, or UART).
• Set the pool address, wallet address, and worker name:

  {
    "pool": "stratum+tcp://pool.kaspa.org:4444",
    "user": "kaspa:your_wallet_address",
    "worker": "fpga01",
    "device": "/dev/ttyUSB0"
  }

• Launch the miner:
  ./kaspaminer --fpga --config config.json
• Monitor output for accepted shares and hash rate. A properly configured FPGA should report 500–800 MH/s depending on model and optimization.

Ensure the baud rate and serial port settings match those defined in the FPGA core. Mismatched settings will prevent communication and result in “no response from device” errors.

Troubleshooting Common FPGA Mining Issues

Even with correct setup, issues may arise. Below are frequent problems and their solutions:

• FPGA not detected by host software: Verify USB-to-UART bridge drivers are installed (e.g., FTDI or CP2102). Use lsusb and dmesg | grep tty on Linux to confirm device detection.
• Low or zero hash rate: Check if the FPGA design was optimized for kHeavyHash. Some cores require manual adjustment of pipeline stages or memory access patterns.
• Overheating or instability: Ensure adequate cooling. FPGAs like Kintex-7 can draw significant power under load. Use a powered USB hub or external power supply if needed.
• Rejected shares: Confirm the pool URL and wallet address are correct. Also, verify that the FPGA firmware supports the current kHeavyHash version, as protocol updates may require core recompilation.

Always consult the GitHub issue tracker of the mining core repository—many problems have already been documented and resolved by the community.

Frequently Asked Questions

Can I use an ASIC instead of an FPGA for Kaspa mining?

Currently, there are no publicly available ASICs optimized for kHeavyHash. The algorithm was designed to be ASIC-resistant, giving FPGAs a competitive edge. Any ASIC-like performance must come from highly optimized FPGA implementations.

Is it possible to mine Kaspa with multiple FPGAs on one PC?

Yes. Each FPGA must be assigned a unique serial port (e.g., /dev/ttyUSB0, /dev/ttyUSB1). Run separate instances of kaspaminer with different config files, or use a multi-device capable fork that supports concurrent FPGA management.

Do I need to recompile the FPGA core if the network difficulty changes?

No. Network difficulty is managed by the mining pool and software client. The FPGA core only computes hashes; it does not handle difficulty adjustment. Recompilation is only needed for algorithm updates or performance tuning.

How do I verify that my FPGA is mining correctly?

Check the miner’s output for continuous “Accepted share” messages. Monitor your wallet on a block explorer like kaspexplorer.io to confirm received rewards. Also, use htop or nvidia-smi (if GPU is present) to ensure the host CPU is not bottlenecking communication.