Nvidia's GeForce RTX 5090 and RTX 5080 graphics cards are slated to hit shelves today. While initial performance reviews have been disappointing for both GPUs, YouTuber der8auer reported issues with his review sample of the RTX 5080 FE, including boot failures and unexpected crashes when operating in PCIe Gen 5.0 mode. On further investigation, Igor's Lab discussed this particular problem, and the cause might boil down to Nvidia's choice of a multi-PCB design for its Founders Edition models.
Cramming 575W of power inside a dual-slot package for the RTX 5090 required some creative engineering solutions. For starters, the RTX 5090 FE features three PCBs rather than one large PCB, one for the PCIe 5.0 x16 connector, one for the video ports, and the main PCB hosting the GB202 package, GDDR7 memory, and power delivery circuitry. We suspect these modular boards have been connected via ribbon cables to not interfere with cooling.
Der8auer's test bench featured the Asus ROG Crosshair X870E Hero and the Ryzen 7 9800X3D. For reference, this same setup was used to benchmark GPUs like the RX 7900 XTX, RTX 4080, RTX 4090, and even the RTX 5090, with no issues whatsoever. At the start, the RTX 5080 reportedly showed no signal. Power-cycling and reseating the GPU multiple times finally got it to work. With all drivers installed, the problem persisted as the GPU was not detected after another reboot. Rinse, repeat and the GPU booted after a lot of trial and error but ran at remarkably slow PCIe x8 Gen 1.1 speeds.
After manually setting the PCIe configuration to x16 Gen 5.0 in the BIOS, plus all the extra restarts, the GPU successfully ran in PCIe 5.0 mode, only to crash/freeze later in Valorant, PUBG, and Remnant 2. These issues may have several if not many suspects, including driver issues, improper BIOS configurations, faulty components; you name it. However, switching to PCIe Gen 4.0 eliminated all these problems. Given that other GPUs worked fine in the same setup, by deduction the problem likely lies with the RTX 5080 FE, in particular, its design.
Igor's Lab noted in his review of the RTX 5090 that signal integrity is crucial for Blackwell GPUs as they use PCIe 5.0, which doubles data transmission speeds to 32 GT/s. Common symptoms of issues with PCIe connectivity include the system failing to initialize the GPU, unexpected crashing, or freezing; the same anomalies that der8auer faced. This issue is especially apparent if you use a riser cable with these GPUs since you'll have to step down to PCIe 4.0 speeds for stability. The tri-PCB architecture of the Founders Edition in-a-way functions as a riser cable and is suspected to degrade signal quality.
As it stands, this is just a theory and not a proven fact. However, if you end up facing the same problem, a simple fix is to force a downgrade to PCIe Gen 4.0 for the GPU in BIOS, which reportedly incurs a minor loss in performance.
