ROG XG Mobile RTX 5090 eGPU Tested with ROG Ally X Delivers Insane Performance
ROG XG Mobile RTX 5090 eGPU Tested with ROG Ally X Delivers Insane Performance
Introduction
The latest ROG XG Mobile eGPU for 2025 brings a desktop‑class RTX 5090 into a compact Thunderbolt 5 enclosure. Paired with the handheld ROG Ally X, the setup promises a dramatic boost over the device’s integrated graphics. In this article we examine the hardware design, connectivity options, benchmark results, and real‑world gaming performance to determine whether this accessory lives up to the hype.
Overview of the ROG XG Mobile eGPU
The new ROG XG Mobile is a small‑form‑factor external GPU dock that houses a laptop‑grade RTX 5090 with 24 GB of VRAM. Unlike traditional eGPU solutions, the power supply is integrated, eliminating the need for a bulky brick. The unit plugs directly into a wall outlet and can also provide Power Delivery (PD) charging to the host device.
Design Highlights
- Compact chassis with a transparent front panel and subtle ROG logo RGB lighting.
- Built‑in kickstand for stable desktop placement.
- Exhaust vent on the left side dedicated to the GPU.
- Full‑size SD card reader (UHS‑I, up to 312 MB/s) on the top.
- Rear I/O includes:
- 5 Gbps LAN port
- HDMI 2.1
- DisplayPort 2.2
- Two USB 3.2 Gen 2 Type‑A ports
- Dual Thunderbolt 5 ports (upstream and downstream)
Inside the box you receive the dock, a power cord, and a Thunderbolt 5 cable.
Connectivity and Bandwidth
The ROG Ally X uses a USB 4 controller (not USB 4 V2), limiting theoretical throughput to 40 Gbps. In practice, the eGPU achieved about 30 Gbps over this link. By contrast, a laptop equipped with native Thunderbolt 5 (the ROG Strix 18) reached 41 Gbps, roughly 10 Gbps higher.
While the raw numbers seem modest, the extra bandwidth can translate into 30–40 additional FPS in bandwidth‑sensitive scenarios, making Thunderbolt 5 a noticeable advantage over older standards.
Synthetic Benchmark Results
Laptop with Internal RTX 5090 (Thunderbolt 5)
| Benchmark | Total Score | Graphics Score |
|---|---|---|
| 3DMark Time Spy | 22,779 | 24,387 |
| 3DMark Steel Nomad | 6,111 | 60.12 FPS |
Same Laptop Using the External RTX 5090 via Thunderbolt 5
| Benchmark | Total Score | Graphics Score |
|---|---|---|
| 3DMark Time Spy | 21,623 | 22,980 |
| 3DMark Steel Nomad | 5,957 | 59.58 FPS |
The loss in synthetic performance is minimal—typically under 5 %—demonstrating that the external GPU delivers almost the same raw power as its internal counterpart when connected via Thunderbolt 5.
Real‑World Performance on the ROG Ally X
Geekbench 6 OpenCL Test
- Integrated Radeon 8900 iGPU: 38,034 points
- External RTX 5090: 162,074 points
The eGPU provides a >4× improvement in compute capability.
3DMark Scores on the Ally X
| Benchmark | Total Score | FPS |
|---|---|---|
| Time Spy (iGPU) | 3,983 | — |
| Time Spy (RTX 5090) | 18,162 | — |
| Steel Nomad (iGPU) | 592 | 5.92 FPS |
| Steel Nomad (RTX 5090) | 5,635 | 56.35 FPS |
These results confirm a 10‑fold jump in graphics performance when the external GPU is attached.
Gaming Benchmarks
All games were run at 1440p unless noted otherwise, with DLSS settings varied to showcase the impact of AI upscaling and frame generation.
- Doom Eternal (Nightmare, DLSS Quality) – ~70 FPS
- Marvel Rivals (Ultra, DLSS Quality) – ~101 FPS (target 120 FPS)
- Forza Horizon 5 (Extreme, no scaling) – >130 FPS; at 4K the same settings deliver ~82 FPS
- Borderlands 4 (Very High, DLSS‑4 Frame Generation ×4) – >200 FPS
- Cyberpunk 2077 (Ultra, DLSS Quality) – ~76 FPS; with DLSS‑4 Frame Generation ×4 the average climbs to >200 FPS
The RTX 5090 paired with DLSS‑4 frame generation consistently pushes frame rates well beyond 200 FPS in demanding titles, confirming that the eGPU can handle high‑end gaming on a handheld device.
Power Consumption Insights
Monitoring via MSI Afterburner showed the ROG Ally X APU drawing around 35 W under load, while the XG Mobile dock supplied up to 150 W to the GPU. This power envelope is sufficient for sustained high performance without throttling.
Future Outlook and Compatibility
The reviewer plans to test the dock with devices supporting USB 4 V2 (up to 80 Gbps) and explore Thunderbolt 5’s Thunderbolt Share feature on downstream ports. These experiments will clarify whether newer host interfaces can further close the performance gap between internal and external GPUs.
Conclusion
The ROG XG Mobile RTX 5090 eGPU delivers desktop‑class graphics to the ROG Ally X and Thunderbolt 5‑enabled laptops with negligible synthetic performance loss. Real‑world gaming tests show dramatic FPS gains, especially when leveraging DLSS‑4 frame generation. With a sleek design, integrated power supply, and a rich I/O suite, this eGPU stands out as a compelling accessory for users seeking high‑end performance on portable hardware.
Key takeaways:
- Minimal performance penalty over internal RTX 5090 when using Thunderbolt 5.
- Over 4× compute boost in OpenCL workloads.
- Consistently 70‑200 FPS in modern AAA titles at 1440p.
- Future USB 4 V2 and Thunderbolt 5 features may unlock even higher bandwidth.
The ROG XG Mobile proves that external GPUs are no longer a niche solution but a viable path to power‑hungry gaming on handheld and thin‑and‑light laptops.