PCIe Lane Sentinel

Detect PCIe bottlenecks your motherboard manual warned you about — but you never read.

PCIe Lane Sentinel is a Windows desktop app that detects PCIe lane bottlenecks caused by hardware bifurcation — specifically the common scenario where placing an NVMe drive in the wrong M.2 slot drops your GPU from PCIe x16 to x8 without any warning.

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The Problem

Modern AMD and Intel motherboards share CPU PCIe lanes between the primary GPU slot and adjacent M.2 slots. When you populate a specific M.2 slot, the motherboard controller automatically splits the x16 slot into two x8 connections. Your GPU ends up running at half its potential bandwidth — silently, with no warning in Windows.

Windows itself cannot detect this. The PnP API reports the slot's potential, not the actual negotiated link width. GPU-Z can see it — and this app uses GPU-Z's shared memory interface to read the real values directly from PCI config space registers.

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Features

• 🔍 True bifurcation detection — reads GPU PCIe link width directly from hardware registers via GPU-Z shared memory (not Windows PnP API estimates)
• 💾 NVMe drive identification — shows real drive model names (e.g. "Samsung 990 Pro 2TB") instead of generic "Standard NVM Express Controller"
• 🖥️ Motherboard panel — displays your board make/model with one-click links to the PCIe lane map, PDF manual, and manufacturer support page
• ⚠️ Bottleneck alerts — cards highlight in red when a GPU or NVMe is throttled, with a plain-English explanation of why
• 🏷️ Dual data source badges — "GPU-Z Verified" vs "Windows PnP" so you know how reliable each reading is
• ⚡ Real-time refresh — re-scan at any time; run a GPU benchmark first for accurate active link width
• 🪟 Standalone Windows app — packaged as a native .exe via Tauri (no Node.js or terminal needed to run)

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Screenshots

Dashboard showing GPU running at x8 in an x16 slot due to NVMe bifurcation:

AMD Radeon RX 9070           [GPU-Z Verified] [THROTTLED]
PCIe Link Width: x8 / x16 max  ████████░░░░░░░░
PCIe Speed: Gen 5 (32 GT/s)
⚠ Bottleneck Detected: Running at x8 but capable of x16.
  Caused by PCIe bifurcation — an M.2 drive is sharing CPU lanes
  with the GPU slot. Check your motherboard manual below.

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Requirements

To run the pre-built .exe

• Windows 10/11 x64
• GPU-Z running in the background (for accurate GPU bifurcation detection)

Note on architecture: The application relies on native Tauri Rust hooks and powershell scripts to probe hardware securely. No external backend is required! See ARCHITECTURE.md for details.

To build from source

• Node.js ≥ 18 (for compiling the React frontend via Vite)
• Rust (stable toolchain)
• Windows 10/11 x64

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Quick Start

Option A — Browser Dashboard (Dev Mode)

git clone https://github.com/kaiserc/PCIeCheck.git
cd PCIeCheck
pnpm install
pnpm run tauri:dev

This will launch the live-reloading Tauri desktop application. Make sure GPU-Z is open in the background for bifurcation detection.

Option B — Build the Windows .exe

pnpm install
pnpm run tauri:build

The installer will be at:

src-tauri\target\release\bundle\nsis\PCIe Lane Sentinel_0.2.0_x64-setup.exe

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How It Works

Layer	What it does
GPU-Z Shared Memory	Opens the Local\GPUZShMem shared memory segment that GPU-Z populates with real PCI config space register values. This is the only way to read the actual negotiated link width without a kernel driver.
Windows PnP API	PowerShell queries Get-PnpDeviceProperty on PCIe bridge devices to get topology, NVMe controller relationships, and device names.
WMI	Get-PhysicalDisk provides actual NVMe drive model names (Samsung 990 Pro) to replace generic Windows controller names.
React Frontend	Merges both data sources — GPU-Z data overlaid onto PnP topology by matching PCIe generation speed — then renders the dashboard.

For a full technical deep-dive, see docs/HOW-IT-WORKS.md.

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Project Structure

PCIeCheck/
├── src/                    # React + TypeScript frontend
│   ├── App.tsx             # Main dashboard, data fusion logic
│   └── index.css           # Dark-mode UI styles
├── scripts/                # Diagnostic scripts payload
│   ├── get-pci-data.ps1    # PowerShell: Windows PnP bridge scan
│   ├── get-gpuz-data.ps1   # PowerShell: GPU-Z shared memory reader (C# inline)
│   └── get-system-info.ps1 # PowerShell: Motherboard, CPU, NVMe names
├── src-tauri/              # Tauri (Rust) desktop wrapper and backend controllers
│   ├── src/lib.rs          # Tauri app entry point + routers
│   ├── src/commands.rs     # Native Async Rust scripts runner
│   └── tauri.conf.json     # App config, window size, bundle targets
└── docs/
    ├── ARCHITECTURE.md     # System design and data flow
    └── HOW-IT-WORKS.md     # Technical deep-dive

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Scripts

Command	Description
pnpm run dev	Frontend only (Vite HMR)
pnpm run tauri:build	Build production .exe + .msi installer
pnpm run tauri:dev	Tauri dev window (live-reload)

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Tauri Commands (IPC)

The Rust backend securely exposes these functions to the React frontend component:

Endpoint	Description
get_pci_data	All PCIe devices from Windows PnP (GPUs, NVMe, bridges)
get_gpuz_data	GPU PCIe data from GPU-Z shared memory (bifurcation-aware)
get_system_info	Motherboard make/model, CPU name, NVMe friendly names

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Contributing

See CONTRIBUTING.md.

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License

MIT — see LICENSE.

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Acknowledgements

• GPU-Z by TechPowerUp — the shared memory API that makes accurate bifurcation detection possible
• Tauri — for making Rust-powered native Windows apps painless
• The countless builders who discovered their GPU was running at x8 after the build