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Slow USB Speeds (Limited to USB 2.0) on Thunderbolt Ports – ROG Strix Scar 16 (2025)

zygote_rog
Level 8

‎06-08-2025 11:26 PM

When connecting external USB SSD enclosures to any of the Thunderbolt ports, the reported speeds are very slow, around ~35 MB/s. This suggests the ports are likely failing to negotiate the correct speed and are falling back to USB 2.0 compatibility.

I've tested two different enclosures. Both work without any slowdowns when connected to the USB Type-A ports, reporting speeds of up to ~1000 MB/s, indicating USB 3.2 Gen 2 compatibility. The slow USB speeds only occur when using the Thunderbolt ports.

Brand-new Asus ROG Scar Strix 16, RTX 5090, 2025 model.
Windows 11 Pro, reinstalled twice to rule out driver installation issues.
All drivers, firmware, and Windows updates are up to date.

I've found other people reporting the same issue:

 
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2 REPLIES 2

Anbby_ROG
Customer Service Agent

a month ago

Thank you for reporting this issue. You mentioned that you tested two different enclosures and the problem only occurs when using the Thunderbolt port.

Could you please assist us by recording a short video showing the read speed issue and uploading it to a cloud drive? Then, kindly send us a private message with the following information so we can promptly escalate this to the local service team for further investigation. Thank you.

 

  • Serial Number:
  • BIOS Version:
  • Windows Build Version: (Settings - System - About)
  • Are you using any other external devices?
  • SSD Brand/Model:
  • Type-A and Type-C Enclosure Brand/Model:
  • Was a power adapter connected during use?
To speed up issue identification, please provide the product model, BIOS, and driver versions, along with the troubleshooting steps you've already tried to avoid redundant checks.

⚠️ DM are for collecting personal information only. For technical assistance, please post your issue in the discussion thread so everyone can help and share insights! Thank you for your understanding! 🙂
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zygote_rog
Level 8
In response to Anbby_ROG

a month ago

BIOS Version: G635LX.318
Armory Crate: 6.1.18.0
MyASUS: 4.0.36.0
ASUS System Control Interface: 3.1.43.0
NVIDIA Driver:  Nvidia Studio Driver, 576.52, Released Mon, 19, 2025
Intel Graphics: 32.0.101.6881, (2025-04-06)
 
Windows Build Version: (Settings - System - About)
  • Edition: Windows 11 Pro
  • Version: 24H2
  • OS Build: 26100.4351
Are you using any other external devices? No
 
SSD Brand/Model:
  • Primary: Samsung SSD 990 PRO 2TB
  • Secondary: Samsung SSD 990 PRO 4TB
Type-A and Type-C Enclosure Brand/Model:
  • Enclosure 1: FIDECO M.2 NVME SSD Enclosure, 10Gbps USB 3.2 Gen 2
  • Enclosure 2: FIDECO M.2 NVME and SATA External SSD Enclosure, PCIe USB 3.2, Gen 2, 10Gbps Adapter
Was a power adapter connected during use? Yes

 

When connected to the USB4 ports speeds are as expected:

USB-4 port.jpg

2.0 speeds in Thunderbolt port 1:

THB Port 1.jpg

Same with port 2:

THB Port 2.jpg

   

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