Introduction

The AMD next-generation we've long been waiting for is finally here! The new Radeon RX 7900 XTX in this review, and the Radeon RX 7900 XT, which we're also reviewing today, debut the company's 3rd generation RDNA graphics architecture, or RDNA 3. With it, the company is also introducing the world's first chiplet-based GPU in an effort to maximize utilization of the TSMC 5 nm foundry node, without compromising on performance, or too much on power. The RDNA 3 graphics architecture promises a similar 50% leap in performance/Watt over the previous-generation RDNA2, which helped AMD compete in the high-end segment after a long gap of 7-odd years. The new architecture improves in many areas, including compute power, memory sub-system, display engine with support for the latest DisplayPort 2.1 standard, multiple-stream acceleration for the latest video formats, and most importantly, AI acceleration, and a more advanced ray tracing hardware.



AMD's decision to leverage chiplets to build the new "Navi 31" GPU powering the Radeon RX 7900 series, has to do with attempting to keep Moore's Law alive in spirit. The idea is to achieve high-end performance leadership at the same sub-$1000 price-points that we've had before. NVIDIA on the other hand considers Moore's Law dead, and says that it's no longer possible to economically build large high-end GPUs. AMD therefore identified all the components that can do with a slightly older foundry node—such as the L3 cache, memory controllers, and memory PHY, and moved them from the GPU, onto six little dies called MCDs (memory cache dies), which are built on the slightly older 6 nm process. The remaining GPU with all its compute-intensive hardware, would be called the GCD (graphics compute die). The GCD and MCDs would be connected by an extreme bandwidth Infinity Fabric Fanout interconnect, which enables 5.4 TB/s of bandwidth between the GCD and MCDs. Each MCD has a 16 MB segment of the GPU's total 96 MB Infinity Cache, which is a bit smaller than the 128 MB of the previous generation, but made up for by the 87% higher GDDR6 memory bandwidth from the GPU's 384-bit memory bus, handling 20 Gbps-rated memory, for 960 GB/s of bandwidth.

The RDNA 3 graphics architecture which we're reviewing today, introduces dual issue-rate compute units, with a high degree of optimization in the way idle SIMD resources are utilized, support for newer math formats, and a new AI accelerator that retasks the SIMDs for matrix math functions. Together, these optimizations produce a 17% IPC uplift over the previous-generation RDNA2 CU. There are 96 CUs physically present in the silicon, which work out to 6,144 stream processors. The architecture also sees an increase in engine clocks, and a decoupling of the shader clock speeds to those of the GPU's Front End, which operates at a 10-15% higher frequency. The most striking aspect of the RDNA 3 architecture is that the typical board power of these GPUs is well contained, with the RX 7900 XTX rated at just 350 W, and the RX 7900 XT at 315 W—both of which can be fed by just two 8-pin PCIe power connectors, and cooled by solutions much smaller than those you find on the competing NVIDIA GeForce RTX 4080 or RTX 4090 "Ada."

The Radeon RX 7900 XTX we're reviewing here, maxes out the "Navi 31" silicon, featuring all 96 compute units, or all 6,144 stream processors, 96 second generation Ray Accelerators, 384 TMUs, a whopping 192 ROPs, and the GPU's whole 384-bit memory interface, holding 24 GB of 20 Gbps-rated GDDR6 memory. All this for "just" $1,000, or the same price the previous-generation RX 6900 XT debuted at. This is where AMD's choices with the chiplet architecture begins to make sense, as both of NVIDIA's competing GPUs are priced much higher.

We also have a second Navi 31 review for you today: the Radeon RX 7900 XT.

AMD RDNA 3 Graphics Architecture

The Radeon RX 7900 XTX and RX 7900 XT debut AMD's 3rd generation RDNA graphics architecture, termed RDNA 3. With it, AMD plans to repeat the generational 50% performance/Watt gain it achieved with RDNA2, which sprung it back to the high-end graphics segment after a long gap. AMD claims it succeeded in this endeavor, with a 54% generational performance/Watt gain. At the heart of this effort is the switch to the new TSMC 5 nm EUV foundry node. AMD figured out early on that it cannot build large monolithic GPUs on 5 nm without thinning its margins in the fight against NVIDIA, and set out to innovate the Chiplet architecture for the GPU. Under this, specific parts of the GPU that actually benefit from a switch to a newer foundry node, such as the Shader Engines, would be built on a centralized 5 nm die called the Graphics Compute Die (GCD), while those components that can make do with a less advanced node, namely the memory controllers and L3 cache, would be spun off to chiplets called Memory Cache Dies (MCDs), built on 6 nm.


The "Navi 31" GPU is hence a chiplet GPU and not a multi-chip module like "Vega 10." In a chiplet-based device, various components that can otherwise not exist on their own packages, are placed on a single package, with the goal of minimizing production costs, by stratifying their need for a new foundry node, such that only the most power-intensive IP receive the most advanced node. In a MCM, chips that can otherwise exist on their own package, are combined onto a single package for conserving PCB real-estate, or reducing latency. The GCD in the "Navi 31" GPU hence has all the shader engines, caches up to L2, the front-end Command Processor, Async Compute Engines (ACEs), the Display Engine, and the Media Engine. Each of the six MCDs has a 64-bit wide memory bus, and a 16 MB segment of the GPU's 96 MB Infinity Cache memory. The size of the Infinity Cache may have been generationally reduced (compared to 128 MB on "Navi 21"), but AMD has widened the memory bus itself, from 256-bit up to 384-bit.


Much of the architectural innovation is not with the chiplet design (a packaging innovation); but at the level of the RDNA 3 Dual-Compute Unit (or Compute Unit pair). The "Navi 31" GPU physically features 96 compute units spread across six Shader Engines. AMD claims that at the same engine clocks, the RDNA 3 CU offers a 17.4% IPC increase over the RDNA2 CU. There are 20% more CUs over the "Navi 21," and these run at higher engine clocks, tapping into the power headroom afforded by the 5 nm process. These combined work out to the 54% generational performance uplift, with which AMD plans to retain competitiveness with NVIDIA's RTX 40-series "Ada" high-end SKUs.


The new RDNA 3 CU introduces multi-precision capability for the 64 stream processors per CU: operating either as 1x SIMD64 or 2x SIMD32 units. The Vector Unit that houses these SIMD units can either function as a SIMD execution mechanism, or as a Matrix execution unit, thanks to the new AI Matrix Accelerator, which provides a 2.7x matrix multiplication performance uplift versus conventional SIMD execution. Also added are support for the Bfloat16 instruction-set, and SIMD8 execution. The GPU hence enjoys AI hardware-acceleration that can be leveraged in future feature-additions relevant to gamers, such as FSR 3.0. Game developers will also look for ways to exploit accelerated AI, now that all three brands feature it (NVIDIA Tensor cores and Intel XMX cores).


AMD's first-generation Ray Accelerator, introduced with the RDNA2 architecture, was the result of a hasty effort to catch up to NVIDIA with a DirectX 12 Ultimate GPU, where they developed a fixed-function hardware to calculate ray intersections, and offloaded a large chunk of RT processing to the generationally-doubled SIMD resources. With RDNA 3, they've refined the Ray Accelerator to achieve an 80% ray tracing performance uplift over the previous generation, when you add up the Ray Accelerator count, their higher engine clocks, and other hardware-level optimizations, such as early sub-tree culling, specialized box sorting modes, and reduced traversal iterations.


There is a 50% ray intersection capacity improvement for the "Navi 31" GPU thanks to these optimizations, and cycles-per-ray reduction. Besides these, AMD has also made several improvements to the geometry- and pixel-pipes, with the introduction of the new multi-draw indirect accelerator (MDIA), which reduces CPU API and driver-level overheads by gathering and parsing multi-draw command data. At the hardware-level 12 primitives per clock is now supported compared to 8 per clock on RDNA2, thanks to culling. The core-configuration overall enables 50% more rasterized performance per clock.

The GCD features six Shader Engines, each with 16 compute units (or 8 dual compute units), which work out to 1,024 stream processors. Six such Shader Engines make up 6,144 stream processors with 96 Ray Accelerators and 96 AI Accelerators. The GPU has 384 TMUs, and a massive 192 ROPs—a 50% increase over "Navi 21." The Radeon RX 7900 XTX enables all 96 CUs, and maxes out the silicon, whereas the RX 7900 XT has 84 out of 96 CUs enabled, which work out to 5,376 stream processors, 84 Ray Accelerators, 336 TMUs, and an unchanged 192 ROPs. The RX 7900 XTX gets 24 GB of GDDR6 memory across the GPU's entire 384-bit memory bus, with a memory speed of 20 Gbps (GDDR6-effective), translating to 960 GB/s of memory bandwidth. The RX 7900 XT is equipped with 20 GB of memory across a narrower 320-bit memory bus carved out by disabling one of the six MCDs. At the same 20 Gbps speed, this yields 800 GB/s bandwidth.


AMD has significantly improved the Display Engine of "Navi 31" over the previous-generation in terms of connectivity. The new Radiance Display Engine comes with native support for DisplayPort 2.1, which enables 8K output at up to 165 Hz refresh-rate, or 4K at up to 480 Hz, with a single cable. AMD has refined its FSR 2 algorithm to support 8K (i.e. render at a lower resolution with FSR-enhanced upscaling), to make it possible to enjoy the latest AAA titles at playable frame-rates on 8K displays. Both the RX 7900 series cards get two full-size DP 2.1 connectors, besides an HDMI 2.1b, and a USB-C with DP 1.2 passthrough. The "Navi 31" silicon receives full hardware-accelerated AV1 encode and decode capabilities, through dual independent encode/decoders, so two independent video streams can be simultaneously transcoded, or one stream at twice the framerate. With this generation, AMD is also introducing SmartAccess Video, a feature that lets the AMD driver leverage the hardware encoders of the RDNA2 iGPU of Ryzen 7000 desktop processors, for additional encoding performance.

Packaging

The Card

The AMD Radeon RX 7900 XTX looks fantastic. AMD has refined their design approach even further, the card is dominated by black in various shades of gray. On the metal backplate you get some red highlights, and three fins on the side have been painted red to represent the third generation of the RDNA architecture.


AMD has illuminated three pieces of the cooler, around the central fan, the default is white, but the lighting can be adjusted. The 7900 XT has no RGB lighting.


Dimensions of the card are 28.0 x 12.5 cm, and it weighs 1809 g.


Here's various comparisons to other relevant cards. The RX 7900 Series is clearly much more compact than the offerings from NVIDIA.


The Radeon RX 7900 XT is slightly smaller than the XTX.


Installation requires three slots in your system.


Display connectivity includes two standard DisplayPort 2.1 ports (RDNA2 had 1.4a) and one HDMI 2.1a (same as RDNA2). The USB-C port that you see is not a classic USB port that you can attach storage to, it only supports DisplayPort 2.1 passthrough + PD, for use with VR.

AMD has upgraded their encode/decode setup. It now comes with two independent hardware units that can encode and decode two streams of video in parallel, or one stream at double the FPS rate. There's support for VP9, H.264, H.265 and AV1 decode, and encoding is supported for H.264, H.265 and AV1.


The card uses a classic dual 8-pin power input config, rated for 375 W maximum power. NVIDIA on the other hand uses the new 12+4 pin ATX 12VHPWR connector, which is rated for up to 600 W of power draw. This makes it easy to install the AMD card in older systems, but it does limit their maximum current delivery capability. Some custom board designs of the RX 7900 XTX will have three power inputs.

Teardown

Taking the RX 7900 XTX apart is really easy, it's straightforward to disassemble and maintain.


The main heatsink provides cooling for the GPU chip, memory chips and VRM circuitry.


After removing the fan assembly, we can see that AMD is using a very large vapor-chamber that has fins directly attached to it. There's no heatpipes in use.


The backplate is made from thick metal and of excellent build quality. It protects the card against damage during installation and handling.

High-resolution PCB Pictures

These pictures are for the convenience of volt modders and people who would like to see all the finer details on the PCB. Feel free to link back to us and use these in your articles, videos or forum posts.


High-resolution versions are also available (front, back).