September 30, 2022

AMD Radeon RX 7900 XT PCB Layout: Navi 31 GPU, 7 Chips, up to 450W

NVIDIA’s next-gen GeForce RTX 40-series “Ada Lovelace” GPUs are launching next week, and while we’re hearing a mountain of information about Ada, RDNA 3 isn’t hiding too far away.

AMD’s next-generation RDNA 3-based Radeon RX 7900 XT flagship GPU has been teased, based on the upcoming Navi 31 GPU and now posing for the camera in a new way: a leaked PCB schematic from Igor’s Lab shows off the Radeon RX 7900 XT in all its next-gen GPU glory.

SEE THE GALLERY – 3 IMAGES

The new leaked Radeon RX 7900 XT PCB shows us what should be very close to the RX 7900 XT reference design, where Igor placed 3 x 8-pin PCIe power connectors on the PCB schematic. With each of the 8-pin connectors capable of 150W, the three here will chew up to 450W (and 75W from the PCIe 4.0 x16 slot, if AMD is using Gen4).

We can see this beautiful new Navi 31 “RDNA 3” GPU right in the middle of the PCB, consisting of 7 chiplets in total (1 x GCD and 6 x MCD). The GCD is expected to measure 308mm2 while the MCDs will measure 37.5mm2 each, rounding up the total case area to 225mm2. That’s a die size of 538mm2 for the entire case.

Around these 7 chiplets we can find 12 GDDR6 memory modules, capable of taking up to 16 GB of DRAM modules for a total of 24 GB of GDDR6 memory on AMD’s next-gen Radeon RX 7900 XT graphics card.

AMD is reportedly using a 21+3 phase power system with 16 voltage converters (from 8 phases working in parallel) for its Navi 31 based Radeon RX 7900 XT graphics card. This is an upgrade large out of the 16 phases used by AMD on the Radeon RX 6900 XT, which is why power requirements have increased (3 x 8-pin PCIe power connectors versus 2 x 8-pin PCIe power connectors).

The new Radeon RX 7900 XT should have a maximum card power of 450W but doesn’t need to come close (especially in the Radeon RX 7900 XT reference form). We should see custom variants of the Radeon RX 7900 XT such as SAPPHIRE, MSI, XFX, PowerColor, etc. pushing this Navi 31 to its limits and testing the card’s maximum power of 450W.

AMD Radeon RX 7900 XT PCB layout: Navi 31 GPU, 7 chips, up to 450W 05 |  TweakTown.com

AMD Current Generation Radeon RX 6900 XT Reference PCB

Igor also notes that in the purported board design there are 6+2 sockets instead of the 12VHPWR, with Igor noting that he “will leave it open if that PCIe 5.0 slot comes to the final boards”. Igor also notes that there are “a total of three tracks on the board’s PCIe external power supply and each of the tracks has an LC combination of coil and polymer caps upstream as output filtering against spikes high frequency load”.

Igor breaks down his Radeon RX 7900 XT info, with all the juice below:

  • The RX 7900XT’s Navi31 GPU relies on a total of 6 chiplets (I’ll leave the detailed data to the Twitter kings here, but they’ve been pretty good lately)
  • 12 GDDR6 modules are used, suggesting memory expansion up to 24 GB
  • There are (in addition to 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 power supply scheme: 16 voltage converters (from 8 phases operating in parallel) for VDC_GFX, 2x memory, 2x VDD_SOC and 1x VDDCI. The card would therefore be delivered with 8 phases, which is in line with the general trend (also at NVIDIA). By the way, this is not speculation, but a real circuit design, but I don’t want to go into details.
  • In the left third are the various voltage transformers for the partial voltages and below the row of voltage transformers also the input filtering for the slot (12 volts and 3.3 volts), which I also omitted 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 feed the board’s voltage converters and each of the tracks has an LC combination of coil and polymer caps upstream as output filtering against high frequency load spikes
  • In the alleged board design, we see three 6+2 sockets instead of the 12VHPWR. I will leave open if this PCIe 5.0 connector will be integrated into the final boards.
  • However, this also limits the card’s maximum power to 450 watts, with the actual TBP expected to be well below this.


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