AMD Navi 31 (RDNA 3): A look at the putative PCB of the Radeon RX 7900 XT

While Nvidia is likely to lift the curtain on GeForce RTX 4000 in five days after months of wildest speculation and leaks have recently become more concrete, AMD’s Radeon RX 7000 with RDNA 3 architecture has recently been very quiet again. Igor’s Lab ends the silence with a schematic of the PCB of a Radeon RX 7900 XT.

Drawing based on reliable sources

With critical reference to the leak competition on Twitter and the dispute that repeatedly prevails between the parties involved, Igor’s Lab cites a large number of reliable sources as the basis for the specially created drawing – the probability that what is shown corresponds to reality is high to classify. The drawing represents “the lowest common denominator” of the available photos, CAD drawings, and descriptions. It is intended to show a so-called custom design, although this should be close to AMD’s reference.

Custom designs are the basis

The fact that three 8-pin PCIe connectors are soldered on the circuit board fits the custom design character, while it was recently assumed that AMD would get by with two 8-pins on the reference designs. With two of these sockets, however, the power loss should not be much higher than 300 watts (150 watts per 8-pin connection plus a maximum of 75 watts via PCIe) and custom designs should be higher, they are already doing it today.

In all likelihood, AMD will not yet rely on the new 12(+4)-pin 12VHPWR connector, which allows up to 600 watts via just one cable strand. However, there is no certainty on this point. At Nvidia, both the Founders Edition and custom designs at the upper end of the performance range should all be based on the new standard.

This is what the PCB of the Radeon RX 7900 XT should look like in the reference design (Image: 
Igor’s Lab)

According to Igor’s Lab, custom designs of the Radeon RX 7900 XT could use up to 21 voltage converters, 16 of which provide the main voltages VDDC_GFX, memory, VDD_SOC, and VDDCI in doubled 8 phases, while five more provide the secondary voltages. This is not speculation but secured on the basis of existing circuit designs.

Navi 31 with 6+1 chiplets

Furthermore, the scheme confirms the structure of Navi 31, which was already credibly traded in the rumor mill, consisting of a graphics compute die (processing unit) and six memory control dies (memory chip including Infinity Cache).

Of the six memory controllers, two 2 GB GDDR6 chips each are to be addressed via 32 bits each, which results in 24 GB via a 384-bit interface. One HDMI and three DisplayPort ports are to be offered as connections.This is what AMD’s RDNA 3 GPUs could look like

GPUNavi 31GPS 32GPS 33
codenamegfx1100
(“Plum Bonito”)
gfx1101
(“Wheat Nas”)
gfx1102
(“Hot Pink Bonefish”)
designChiplet
1 × GCD + 6 × MCD
(~308 mm², 6 × ~37.5 mm²)
Chiplet
1 × GCD + 4 × MCD
(~200 mm², 4 × ~37.5 mm²)
Monolithic
One chip (~203 mm²)
productionTSMC N5 (GCD), TSMC N6 (MCD)TSMC N6
GCD configuration48 WGPs with 12,288 ALUs30 WGPs with 7,680 ALUs16 WGP with 4,096 ALUs
Infinity cache96MB or 192MB
(6×16 or 6×32MB)
64MB
(4 × 16MB)
32MB
memory interface384-bit GDDR6256-bit GDDR6128-bit GDDR6
GCD= Graphics Compute Die (processing unit)
MCD = Memory Control Die (memory chip including Infinity Cache)

Radeon RX 7000 will be released in 2022

AMD recently confirmed that RDNA 3 will be launched later this year and showed a working system with Ryzen 7000 and RDNA 3 GPU. However, AMD has not yet given exact dates or products.

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