StarTech PEXUSB311AC3 PCIe USB 3.2 Gen 2 Expansion Card (USB-A + USB-C, 10Gbps)

Overview

The StarTech PEXUSB311AC3 is a single-slot PCI Express expansion card that adds two USB 3.2 Gen 2 ports — one USB-A and one USB-C — to any desktop workstation, server, or NVR with an available PCIe x4 slot. The defining characteristic here is sustained 10Gbps throughput on both ports simultaneously, thanks to the ASMedia ASM3142 chipset's ability to maintain full-speed operation on each port independently, even when both are active with devices running at different USB speeds. If you've dealt with earlier PCIe USB cards that throttle shared bandwidth the moment you mix a Gen 1 device with a Gen 2 device, this card addresses that directly.

For security and AV-over-IP integrators, the card slots cleanly into StarTech's expansion card lineup and fits the common scenario of adding fast USB 3.2 capability to a dedicated recording workstation or forensic analysis machine without replacing the host system.

Key Features

• Dual 10Gbps USB 3.2 Gen 2 Ports: Both the USB-A and USB-C ports operate at up to 10Gbps independently. When you're offloading high-resolution video from a camera or copying evidence-grade footage to external storage, you're not sharing a single lane between both ports — each gets its own path to the ASM3142 controller. That matters on a forensic workstation where speed affects how long an analyst waits.
• Mixed-Speed Device Support Without Throttling: Plug a USB 3.2 Gen 1 (5Gbps) device into one port and a Gen 2 (10Gbps) device into the other. The ASM3142 controller handles the negotiation per-port, so the faster device doesn't get dragged down to the slower device's speed. This is the core use case the card is designed for — mixed peripheral environments common in operational IT and security workstations.
• PCIe x4 Interface (PCIe 3.0): The card seats in a PCIe x4 or larger slot and uses PCI Express Base 3.0 signaling, which provides far more than enough upstream bandwidth to support both USB 3.2 Gen 2 ports at full speed simultaneously. If your motherboard or NVR only has PCIe x8 or x16 slots open, the card installs there as well — PCIe is backward compatible in slot size.
• Optional SATA Power Connector for Bus-Hungry Devices: The card includes one internal SATA power connector. USB-C devices that draw significant bus power — external SSDs under load, certain industrial USB peripherals — benefit from this supplemental power path. It prevents the host system's PCIe slot from bearing the entire power burden, which matters in chassis with tight power budgets.
• USB-C Port at Full USB 3.2 Gen 2 Spec: The external USB-C port is a standard 24-pin USB 3.2 Type-C connector running at Gen 2 (10Gbps). This is relevant when connecting current-generation external drives or USB-C docks. Note: this port provides data and power delivery over USB — it does not carry Thunderbolt or DisplayPort signals, so plan accordingly if your peripheral requires those protocols.
• Broad OS Support — Windows, Linux, macOS: The card operates across Windows, Linux, and macOS without exotic driver requirements. For integrators deploying Linux-based NVR appliances or forensic workstations running Ubuntu or similar, this matters — many PCIe expansion cards require Windows-only driver packages that simply don't work in production Linux environments.
• Compact Form Factor for Dense Installs: The PCB measures 12.0 cm × 8.1 cm × 2.1 cm and weighs 48g, which is relevant in rackmount workstations and compact NVR chassis where adjacent slot clearance is tight. A low-profile bracket is not mentioned in evidence — verify your chassis requirements before ordering if the system uses a small-form-factor case.
• Operational Temperature Range 5°C to 50°C: Rated for standard indoor operating environments. This covers typical server room and workstation deployments. It is not rated for extended cold storage or industrial environments below 5°C while powered — factor that in for edge deployments in unheated spaces.

Integration & Compatibility

The PEXUSB311AC3 targets workstations and servers in the PCIe expansion card category that need USB 3.2 Gen 2 capability added post-purchase. Common deployment contexts include video surveillance workstations used for evidence transfer, NVR host machines that need fast external storage ports, and IT refresh projects where the motherboard predates USB 3.2 Gen 2 onboard support.

The ASMedia ASM3142 is a proven, well-supported chipset with driver coverage across current Windows releases, mainstream Linux distributions, and macOS. For integrators building out network video recorder workstations or forensic review stations, this chipset compatibility reduces the risk of driver conflicts in mixed OS environments. Pair it with a PoE switch and appropriate cabling infrastructure when the workstation is part of a larger IP camera network build — see the PoE switch selection guide for switch sizing considerations.

One practical note: the card requires a PCIe x4 slot (or larger). Before specifying this card for a rackmount server or compact NVR chassis, verify available slot types — x1 slots will not accept this card physically or electrically.

Frequently Asked Questions

Q: What PCIe slot size does the PEXUSB311AC3 require?

A: The PEXUSB311AC3 uses a PCIe x4 interface. It installs in any PCIe x4, x8, or x16 slot — larger slots are physically and electrically compatible. It cannot be installed in a PCIe x1 slot.

Q: Does the USB-C port on the PEXUSB311AC3 support Thunderbolt or DisplayPort?

A: No. The USB-C port is a USB 3.2 Gen 2 data and power port only. It does not carry Thunderbolt or DisplayPort signals. If your peripheral requires Thunderbolt, this card is not the correct solution.

Q: Can both ports run at 10Gbps at the same time?

A: Yes. The ASMedia ASM3142 chipset manages each port independently. Both the USB-A and USB-C ports can each sustain up to 10Gbps simultaneously without sharing bandwidth between them.

Q: What operating systems are supported?

A: The PEXUSB311AC3 supports Windows, Linux, and macOS. The ASM3142 chipset has broad driver coverage across these platforms, including mainstream Linux distributions, which matters for Linux-based NVR or forensic workstation deployments.

Q: Is the SATA power connector required for operation?

A: No. The internal SATA power connector is optional. It supplements bus power for USB devices with higher power draw — such as external SSDs under sustained load. The card functions without it, but connecting SATA power is recommended if you're running power-hungry USB-C peripherals.

Q: What is the warranty on the PEXUSB311AC3?

A: The PEXUSB311AC3 carries a 2-year manufacturer warranty.

James Everett

The spec that matters most on the PEXUSB311AC3 is the per-port independent bandwidth architecture driven by the ASM3142 chipset — both the USB-A and USB-C ports sustain up to 10Gbps each, simultaneously, without negotiating shared throughput. In practice, that means a surveillance analyst can be pulling footage off a USB-C external SSD at full Gen 2 speed while a USB-A connected device is also running at Gen 2, and neither port drags the other down. That's the real operational difference versus older single-controller designs.

Technical Highlights:

• ASMedia ASM3142 Chipset: Per-port independent 10Gbps lanes — no bandwidth sharing between the USB-A and USB-C ports under mixed-device load. This is what the 'maintains max speed with mixed speed devices' claim actually means in practice.
• PCIe 3.0 x4 Interface: Upstream bandwidth is not the bottleneck here. PCIe 3.0 x4 delivers roughly 32Gbps of upstream capacity — more than four times the combined maximum of both USB ports at full 10Gbps each. The PCIe link won't limit you.
• Optional SATA Power Input: Supplemental power for USB-C devices that exceed standard bus power thresholds. Worth connecting in forensic workstations where external NVMe enclosures or high-draw USB-C hubs are part of the workflow.

Deployment Considerations:

• Verify slot availability before specifying: this card requires a PCIe x4 or larger slot. Compact NVR chassis and small-form-factor workstations sometimes have only x1 slots open after the GPU and capture cards are installed — confirm the slot inventory before the card ships.
• The USB-C port is data + power only — no Thunderbolt, no Alt Mode video. If the deployment workflow involves USB-C display output or Thunderbolt storage, this card won't satisfy that requirement. Scope the peripheral list before committing.

For a forensic video review workstation — where an analyst needs to simultaneously offload footage from a USB-C external drive and run a USB-A connected hardware write-blocker at full speed — the PEXUSB311AC3 is the right card. That mixed-speed, dual-simultaneous-port scenario is exactly what the ASM3142 architecture handles cleanly, and the Linux driver support means it installs without friction on Ubuntu-based forensic platforms.