USB4 40Gbps vs. USB4 80Gbps: A Performance Comparison

by FuMaoquan February 27, 2025

The Universal Serial Bus (USB) standard has evolved dramatically over the years, with each iteration pushing the boundaries of speed, power delivery, and versatility. Among the latest advancements are USB4 40Gbps and USB4 80Gbps, two specifications that promise to redefine connectivity for modern devices. While both are part of the USB4 framework, they differ significantly in performance and capabilities. Below, we break down their key distinctions and explore how these differences impact real-world usage.

1. Bandwidth and Speed

The most glaring difference lies in their maximum theoretical bandwidth:

USB4 40Gbps: As the name suggests, this version supports a maximum data transfer rate of 40 gigabits per second (Gbps). It achieves this by utilizing dual-lane operation over a USB Type-C connector, effectively combining two 20Gbps channels.
USB4 80Gbps: Introduced as part of the USB4 Version 2.0 specification (released in late 2022), this iteration doubles the bandwidth to 80 Gbps under optimal conditions. This is accomplished through advanced signaling technology and improved data encoding (e.g., PAM3 modulation), allowing more data to be transmitted per cycle.

Practical Impact:

A 10GB file transfer could take ~2 seconds with USB4 80Gbps versus ~4 seconds with USB4 40Gbps (assuming no overhead).
For high-resolution video, USB4 80Gbps can support dual 8K displays at 120Hz or a single 16K display, whereas USB4 40Gbps maxes out at dual 4K/60Hz or a single 8K/30Hz configuration.

2. Backward Compatibility

Both standards maintain backward compatibility with older USB and Thunderbolt devices, but there’s a caveat:

USB4 40Gbps: Fully compatible with Thunderbolt 3 and USB 3.2 Gen 2x2 (20Gbps) devices.
USB4 80Gbps: While backward compatible, achieving the full 80Gbps speed requires newly certified cables and ports. Older USB4 40Gbps cables may limit performance to 40Gbps.

3. Power Delivery

Power delivery (USB PD) remains largely unchanged between the two:

Both support up to 240W of power (via USB PD 3.1), enabling fast charging for laptops, monitors, and other high-power peripherals.

4. Use Cases

The performance leap to 80Gbps unlocks new possibilities:

USB4 40Gbps: Ideal for mainstream users needing fast external storage (e.g., NVMe SSDs), mid-tier gaming setups, or single high-resolution displays.
USB4 80Gbps: Tailored for prosumers and professionals requiring:
- Ultra-high-speed data transfers (e.g., 8K raw video editing).
- Advanced multi-display configurations for VR/AR, simulation, or content creation.
- Future-proofing for AI/ML workloads or low-latency external GPU setups.

5. Physical Layer and Cabling

USB4 40Gbps: Uses existing USB Type-C passive cables up to 0.8 meters for full performance.
USB4 80Gbps: Requires active cables or shorter passive cables to maintain signal integrity at higher speeds. Longer cables may throttle bandwidth.

Conclusion: Which Should You Choose?

For most users, USB4 40Gbps remains a robust choice, offering ample speed for everyday tasks. However, USB4 80Gbps represents a significant leap forward, catering to power users and cutting-edge applications. As the ecosystem matures—with compatible devices, cables, and hosts—the 80Gbps standard will likely become the gold standard for high-performance connectivity.

When upgrading, always verify that your hardware (host, device, and cables) supports the desired USB4 tier to fully leverage its capabilities. The future of USB is faster, smarter, and more versatile than ever—and the choice between 40Gbps and 80Gbps hinges on how aggressively you want to embrace that future.

Note: USB4 80Gbps adoption is still in its early stages, with compatible devices expected to proliferate in 2024 and beyond.