With the official launch of Valve’s Steam Machine still on the horizon, the gaming community is buzzing with a mix of excitement and skepticism. The company’s promises of a six-fold GPU performance increase over the Steam Deck and the ability to target 4K 60 FPS gaming have set a high bar. But how will these claims hold up in the real world?
While we wait for final hardware, one intrepid tech enthusiast has taken matters into their own hands. The YouTube channel The Phawx has embarked on an ambitious project: building a compact PC designed to be a near-perfect performance replica of the upcoming Steam Machine. This isn't just about using similar parts; it's a deep dive into replicating Valve’s custom architecture, right down to the CPU behavior, GPU constraints, and power limits.
The Blueprint: Recreating Valve’s Custom APU
The foundation of any performance test is the silicon, and Valve’s Steam Machine is built around a semi-custom AMD Zen 4 APU. The goal was to match its exact configuration: 6 cores, 12 threads, a boost clock up to 4.8 GHz, and a strict 30 W power cap.
To achieve this, The Phawx started with an AMD 8840U laptop processor. By disabling two of its eight cores and parking the corresponding hyperthreads, they arrived at the precise 6-core, 12-thread setup. To mimic the 30 W power budget, the chip was hard-capped at around 4 GHz during demanding all-core workloads, a necessary compromise that mirrors how Valve’s part is expected to perform—hitting the peak 4.8 GHz only in lighter, single-core tasks.
This meticulous approach extended to the cache. A previous Geekbench entry for a mysterious "Val Fremont" device, suspected to be an early Steam Machine, showed a cache structure identical to the 8840U. By parking the correct cores, the creator was able to match the L1, L2, and shared L3 cache. To complete the APU simulation, the integrated GPU was entirely disabled, a move based on the belief that Valve’s custom chip will have its iGPU fused off.
Matching the GPU and System Architecture
For the dedicated graphics, the build uses a Radeon 7600M XT, which shares the same Navi 33 architecture as the GPU expected in the Steam Machine. There’s one key difference: Valve’s chip is predicted to have 28 Compute Units (CUs), while the 7600M XT has 32. To compensate, The Phawx limited the boost clocks to better match the estimated 9 teraflops of Valve's hardware.
The creator notes that the 7600M XT’s extra compute power offers diminishing returns, as memory bandwidth is the primary bottleneck. This suggests Valve’s decision to use a lower-CU GPU might actually be a more balanced design, despite looking weaker on a spec sheet.
The architectural mimicry went even further with the enablement of AMD Smart Access Memory and SmartShift. These technologies, which The Phawx believes Valve will use, allow the CPU and GPU to share a unified power budget. In testing, they found that a restrictive 28 W limit caused both components to downclock aggressively, highlighting the delicate power-balancing act the final Steam Machine will need to perform inside its compact chassis.
To see the full, in-depth build process and technical deep dive, be sure to watch The Phawx's comprehensive video.
Real-World Gaming Performance: The 4K 60 FPS Challenge
With the hardware clone complete, the critical question remained: can it deliver on Valve’s performance promises? The Phawx focused on pushing resolution and frame rate, often sacrificing visual fidelity by using the lowest settings to see how close they could get to that 4K 60 FPS target.
- God of War 3 (RPCS3): Running this demanding emulator at 720p, the system provided a playable, though not locked, 60 FPS experience, offering a realistic look at CPU-bound performance.
- Indiana Jones and the Great Circle: At 4K resolution with all-low settings and XeSS Performance upscaling, the game hovered closer to 30 FPS. The Phawx noted that ray tracing remains particularly demanding for RDNA-based GPUs.
- Starfield: Aiming for 4K 60 FPS with a 50% render resolution and FSR 3 (without frame generation), the system managed 30–40 FPS, with noticeable dips in dense areas like Akila City.
So, what about the claim of being six times faster than the Steam Deck? In GPU-bound scenarios, such as in Returnal, the matched setup came out roughly 6.5 times faster, validating Valve’s performance uplift claim, especially considering the test GPU is slightly more powerful than the one expected in the final product.
After further testing in titles like God of War Ragnarok and Spider-Man: Miles Morales, The Phawx also shares final thoughts and speculates on what all this technical replication could mean for the Steam Machine’s final price tag. The experiment suggests that while Valve's performance targets are ambitious, they are rooted in a solid architectural foundation, setting the stage for a fascinating new contender in the hybrid PC gaming space.
