Sometimes, the most fascinating stories aren’t about finished products; they are about the prototypes—the experimental artifacts that reveal the raw engineering journey of a new technology. This is the case with an intriguing piece of hardware that has surfaced on the secondhand market, offering a glimpse into AMD’s ambitious development process.
A recent find involved a GPU that appeared to be an early engineering sample for what would eventually become the high-end Radeon RX 7900 XTX. It was acquired by tiktoker Shav Tech on the secondary market, but what Shav Tech purchased turned out to be something far more interesting than a standard retail card.
While the seller believed they were purchasing a regular 7900 XTX, the hardware itself told a different story. It was clearly an engineering sample, sporting a distinctive red Printed Circuit Board (PCB)—a hallmark often seen in AMD’s prototypes. Furthermore, this prototype lacked the typical backplate found on retail models.
A closer inspection of the board revealed specialized connectors that tell the story of internal testing and communication. Two extra connectors jutted out from the center of the PCB that are absent from commercially sold cards. One set includes I2C, PMBus, and JTAG headers across both rows. The JTAG connections allow engineers to pull diagnostic data directly from the core memory controller, bypassing internal circuitry for comprehensive testing. Meanwhile, I2C and PMBus facilitate monitoring power draw and temperatures by connecting testers directly to the voltage regulators and telemetry sensors.
Underneath these functional connectors, a shrouded black connector served as a logic analyzer, allowing engineers to capture clean, high-speed signal waves across the PCB traces. This feature was essential for testing die-to-die communication within the MCM design employed by RDNA 3 GPUs before final mass production.
The card also featured little dip switches on the bottom of the PCB, intended to allow testers to switch between PCIe generations and test compatibility with older motherboards. These switches likely served as different boot configurations for recovery VBIOSes.
Adding another layer of intrigue, the prototype was running a custom VBIOS identified as “Navi 31,” refusing to load the VBIOS for the RX 7900 GRE. This detail suggests the card was being used in a context separate from its final commercial release.
The ultimate discrepancy lies in the specifications themselves. While the card was officially recognized in software as a 7900 XTX, its hardware specs did not match the expected high-end model. Instead of the advertised 24GB of GDDR6X VRAM typical for the XTX, this unit only featured 16GB of GDDR6 memory—exactly matching the specifications found on the more performance-focused RX 7900 GRE.
The ROP and TMU counts also aligned with the RX 7900 GRE (160 instead of 192, and 320 instead of 384). This strongly suggests that this piece of hardware was not intended as a standard XTX but rather served as a proof-of-concept for a cut-down version of the Navi 31 silicon. It appears to be one of those valuable experimental cards that helps engineers refine and perfect the next generation of high-performance graphics processing.
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Credit: Tom’s Hardware
