An alleged PCB diagram of what seems to be AMD’s flagship Radeon RX 7900 XT graphics card making use of the top RDNA 3 Navi 31 GPU has been leaked by Igor’s Lab. The graphics card is going to feature a considerable power upgrade over the RDNA 2-based AMD Radeon RX 6900 XT graphics cards.
AMD Radeon RX 7900 XT With Top RDNA 3 Navi 31 GPU Gets Leaked Graphics Card PCB Diagram, Huge Power Delivery Upgrade
The PCB diagram leaked by Igor Wallossek is close to the reference design of the AMD Radeon RX 7900 XT graphics card. It was reported that the flagship RDNA 3 Navi 31 GPU will feature two 8-pin connectors but this PCB seems a little different. It could be likely that this is a partner/AIC reference board while AMD itself will be using a different board themselves.
So starting with the details, we first glance over the Navi 31 “RDNA 3” GPU in the middle of the PCB which is stated to feature 7 chiplets (1 GCD + 6 MCDs). The GCD is expected to measure 308mm2 & the MCDs will measure 37.5mm2 each, rounding up to 225mm2 in total package area. That’s a 538 mm2 die size in its entirety. Surrounding the MCM GPU are 12 GDDR6 memory modules that can reach up to 24 GB capacities using 16Gb DRAM.
An alleged AMD Radeon RX 7900 XT graphics card PCB diagram has been leaked by Igor’s Lab. (Image Credits: Igor’s Lab)
As for the power delivery, the AMD Radeon RX 7900 XT “Navi 31” graphics card is said to feature a 21+3 phase power delivery solution that comprises 16 voltage converters (from 8 phases running in parallel). This alone is a huge upgrade over the 16 phases featured on the Radeon RX 6900 XT & as such, the power requirement has also gone up. Instead of dual 8-pin connectors, this PCB uses triple 8-pin connectors. The card is said to feature a maximum board power or TBP of 450W but the actual figure would be lower than that.
As for display capabilities, the card comes with a single HDMI, and three DP & gets rid of the USB Type-C connector. The full breakdown from Igor is as follows:
The Navi31 GPU of the RX 7900XT relies on a total of 6 chiplets (I’ll leave the detailed data to the Twitter kings here, but they were quite good lately)
12 GDDR6 modules are used, which suggests a memory expansion of up to 24 GB
There are (besides the usual low and partial voltages) 21 large voltage converters installed in my example, which could be divided as follows if AMD keeps the usual supply scheme: 16 voltage converters (from 8 phases running in parallel) for VDDC_GFX, 2x memory, 2x VDD_SOC and 1x VDDCI. The card would therefore be supplied with 8 phases, which is in line with the general trend (also at NVIDIA). By the way, this is not a speculation, but a real circuit design, but I do not want to go into detail.
In the left third there are the various voltage transformers for the partial voltages and below the voltage transformer row also the input filtering for the slot (12 volts and 3.3 volts), which I also left out for the reasons already mentioned.
We recognize 1x HDMI and 3x Displayport, USB-C is not on board
A total of three tracks on the external PCIe power supply supply the card’s voltage converters and each of the tracks has an LC combination of coil and upstream polymer caps as output filtering against high-frequency load peaks
In the presumed board design, we see three 6+2 sockets instead of the 12VHPWR. I’ll leave it open whether this PCIe 5.0 connector will make it onto the final cards.
However, this also limits the maximum board power of the card to 450 watts, whereby the actual TBP should be far below that.
AMD has always tried to go a more standardized route with its PCB and cooling designs starting with the RDNA generation and the Radeon RX 7000 series would also be following these pillars. Following is a Radeon RX 6800 XT reference PCB for comparison:
AMD Radeon RX 7900 XT Graphics Card Specifications
The AMD Navi 31 GPU, the flagship RDNA 3 chip, would power the next-gen enthusiast cards such as the Radeon RX 7900 XT graphics card. We have heard that AMD will drop CU (Compute Units) in favor of WGP (Work Group Processors) on its next-gen RDNA 3 GPUs. Each WGP will house dual CU (Compute Units) but with twice the SIMD32 clusters as opposed to just 2 on each CU within RDNA 2. Rumors are that AMD has the option to select between Samsung and TSMC for the 6nm die.
AMD Navi 31: 12288 Cores, 384-bit Bus, 192 MB Infinity Cache, 308mm2 GPU Die @5nm
AMD Navi 21: 5120 Cores, 384-bit Bus, 128 MB Infinity Cache, 520mm2 GPU Die @7nm
According to the latest information, the AMD Navi 31 GPU with RDNA 3 architecture is expected to offer a single GCD with 48 WGPs, 12 SAs, and 6 SEs. This will give out a total of 12,288 SPs or stream processors. This is an increase of 2.4x in cores compared to the 5120 SPs featured on the Navi 21 GPU. The GPU or the Navi 31 GCD is said to measure 308mm2 and will come packaged on TSMC’s 5nm process node.
The Navi 31 GPU will also carry 6 MCD’s which will feature 16 MB Infinity Cache per die and are also likely to carry the 64-bit (32-bit x 2) memory controllers that will provide the chip with a 384-bit bus interface.
While this equals 96 MB of Infinity Cache which is lower than the 128 MB featured on the current Navi 21 GPUs, there’s also a 3D-Stacked solution in the works which was pointed out recently and that would double the Infinity Cache with 32 MB (16 MB 0-hi + 16 MB 1-hi) capacities for a total of 192 MB of cache. This is a 50% increase versus the current Navi 21 design and it also makes Navi 31 the first GPU with both, chiplet and 3D stacked designs. These chiplets or MCD’s will be fabricated on TSMC’s 6nm process node and measure 37.5mm2 each.
AMD RDNA GPU (Generational Comparison) Preliminary:
GPU NameNavi 10Navi 21Navi 31
GPU Process7nm7nm5nm/6nm
GPU PackageMonolithicMonolithicMCD (Multi-Chiplet Die)
Shader Engines246
GPU WGPs204048
SPs Per WGP128128256
Compute Units (Per Die)4080192
Cores (Per Die)2560512012288
Cores (Total)2560512012288
Peak Clock1905 MHz2250 MHz~3000 MHz
FP32 Compute9.723~75
Memory Bus256-bit256-bit384-bit
Memory TypeGDDR6GDDR6GDDR6
Memory Capacity8 GB16 GB24 GB
Infinity CacheN/A128 MB96-192 MB
Flagship SKURadeon RX 5700 XTRadeon RX 6900 XTXRadeon RX 7900 XT
TBP225W330W350W
LaunchQ3 2019Q4 2020Q4 2022
Yesterday, AMD made a cryptic tweet about how bigger doesn’t necessarily mean better. We tried to decipher what that meant in our post here but rest assured, AMD is getting ready for a launch later this year which will tackle NVIDIA’s flagship GeForce RTX 4090 graphics cards.
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