An NVDA add-on that allows you to manage CPU affinity and process priority for NVDA processes, improving performance on systems with heterogeneous CPU architectures (e.g., Intel CPUs with Performance and Efficiency cores).

Features

CPU Affinity Control: Pin NVDA processes to specific CPU cores
Priority Management: Set process priority from Normal to Realtime
Easy Configuration: Integrated settings panel in NVDA preferences
Automatic Application: Settings are applied automatically when NVDA starts
Child Process Support: Applies settings to NVDA child processes as well

Why Use This Add-on?

Modern AMD Ryzen and Intel CPUs feature a hybrid architecture with:

Performance cores (P-cores): High-performance cores for demanding tasks
Efficiency cores (E-cores): Power-efficient cores for background tasks

NVDA performs significantly better when pinned to Performance cores. This add-on allows you to pin NVDA to your CPU's Performance cores for better responsiveness and set higher process priority so NVDA theoretically gets more CPU time

Installation

Download the .nvda-addon file
Open it with NVDA running (press Enter on the file)
Follow the installation prompts
Restart NVDA

Configuration

Open NVDA Settings (NVDA+N → Preferences → Settings)
Navigate to "CPU Priority Manager" category
Configure the following options:

Settings

Enable CPU Priority Management

Check this box to activate the add-on's functionality.

CPU Cores

Specify which CPU cores NVDA should use, as a comma-separated list (e.g., 4,5,6,7).

Process Priority

Choose the priority level for NVDA processes:

Normal: Standard priority (default Windows behavior)
Above Normal: Higher than normal applications
High: High priority (recommended for most users)
Realtime: Highest priority ⚠️ Use with caution!

Recommended Setting: High Priority

Warning: Realtime priority can make your system unstable if NVDA consumes too much CPU time. Only use this if you understand the implications.

Applying Changes

After changing settings:

Click "OK" or "Apply" to save
Restart NVDA for changes to take effect

The add-on applies settings during NVDA startup, so a restart is required.

How It Works

The add-on uses the psutil library to:

Identify the current NVDA process and its children
Set CPU affinity to restrict execution to specified cores
Set process priority using Windows priority classes

Settings are stored in your NVDA configuration and support configuration profiles.

Troubleshooting

Settings don't seem to apply

Make sure you've restarted NVDA after changing settings
Check the NVDA log (NVDA+F1) for any error messages
Ensure you're running NVDA with sufficient permissions

Invalid CPU cores error

Make sure you're using valid core numbers (0 to N-1, where N is your total logical core count)
Use only numbers and commas, no spaces: 0,1,2,3
The add-on will show your system's total core count in the settings panel

Performance not improving

Verify your CPU actually has Performance/Efficiency cores
Try different core combinations
Check Task Manager to confirm NVDA is running on the specified cores
Consider starting with "High" priority before trying "Realtime"

System becomes unstable

If you set Realtime priority and experience issues:
1. Restart NVDA in safe mode (use nvda.exe --safe-mode)
2. Disable the add-on or change priority to "High"
3. Restart NVDA normally

Configuration Storage

Settings are stored in nvdaConfig\nvda.ini under the [cpuPriority] section:

[cpuPriority]
enabled = True
cpuCores = 4,5,6,7
priorityLevel = HIGH

Logging

The add-on logs all actions to the NVDA log. View the log with NVDA+F1 to see:

When settings are applied
Which processes were configured
Any errors encountered

Building from Source

If you want to build the add-on yourself:

You need python
Clone or download this repository
Install SCons: uv tool install scons
Run: scons in the project directory
The .nvda-addon file will be created in the project root

License

This add-on is licensed under the GNU General Public License v2.0.

Credits

psutil library: Copyright (c) 2009, Jay Loden, Dave Daeschler, Giampaolo Rodola

Contributing

If you think I messed something up, feel free to poke me on Mastodon. I had to close registrations to this forge because of a frankly insane amount of spam BS, so if you want in, let me know and I'll let you in. Alternatively, just fork the thing on your preferred forge and make some edits, tell me about it, and I'll pull in your changes.

Disclaimer

This add-on modifies system-level process settings, so it's entirely possible something might fall over in weird circumstances. Check the safe mode above if you can't get NVDA to run anymore. Also, this is my first time working with NVDA addons. I have very little idea of what I'm doing here as of yet. This addon works for me, it might work for you. That's about all I can say. Always happy to hear of improvements I could make, either on Mastodon or just by email or whatever. You can also hit my Discord at TalonTheDragon.