Alleged AMD Navi PCB Hints at GDDR6 and 256-Bit Bus

Leaked photographs of an unidentified PCB (printed circuit board) originating from the Baidu forums are purportedly for AMD's upcoming 7nm Navi-based gaming graphics card.

Credit: BaiduCredit: Baidu

There's no confirmation that the leaked PCB is indeed for the Navi graphics card, so take the information with a bit of salt. One thing is for sure though, the PCB design is fresh and doesn't seem like any of the PCBs that AMD has used in the past. Assuming that the PCB in question is Navi-based, it's likely an early engineering sample that's commonly used for internal testing only. The final product could still be subject to modifications.


AMD NaviRadeon VIIRX Vega 64RX 590RX 580RTX 2080 Ti
RTX 2080
RTX 2070 / RTX 2060
GTX 1660 Ti / GTX 1660GTX 1650
Architecture
Navi
GCN 5.1
GCN 5.0GCN 4.0GCN 4.0Turing
TuringTuring
TuringTuring
GPU
?
Vega 20Vega 10Polaris 30Polaris 20
TU102
TU104
TU106
TU116TU117
Foundry
TSMC
TSMCGloFlo
GloFlo
GloFlo
TSMC
TSMC
TSMC
TSMCTSMC
Manufacturing Process7nm
7nm14nm12nm14nm
12nm
12nm12nm
12nm
12nm
Transistor Count
?
13.2 billion12.5 billion5.7 billion5.7 billion
18.6 billion
13.6 billion
10.8 billion
6.6 billion4.7 billion
Die Size
200 - 230 mm²331 mm²495 mm²232 mm²232 mm²
754 mm²
545 mm²445 mm²284 mm²200 mm²

The mysterious PCB hosts a pretty small area for the Navi silicon. Current speculation is that the Navi die could measure anything from 200 to 230 mm², which doesn't sound too far-fetched considering that TSMC is reportedly producing Navi for AMD on the foundry's 7nm process node. If the die size is accurate, it will put Navi in the same ballpark as AMD's previous Polaris 20 silicon and Nvidia's present Turing TU117 silicon.

A recent report indicated that the future PlayStation 5 would sport a Navi graphics chip capable of ray tracing. Nvidia already offers real-time ray tracing support on its latest Turing-power graphics card. However, the Green Team's implementation involves baked-in RT cores into the Turing silicon that result in gargantuan dies, so Turing GPUs that lack the RT and Tensor cores are significantly smaller than the full-fledged Turing counterparts. It will be interesting to see how AMD implements ray tracing on Navi given its rumored die size.

Buildzoid PCB Analysis

The alleged Navi die is surrounded by eight spaces reserved for memory chips. This means that the PCB could host an 8GB or 16GB configuration and probably sports a 256-bit memory interface, too. Buildzoid, a respected expert on motherboard and graphics card PCBs, noted that the memory spaces had room for a total of 180 pins (18x5x2), which coincides with the 180 ballout for GDDR6 chips. It's evident that Navi will employ GDDR6 memory.


AMD Navi
Radeon VIIRX Vega 64RX Vega 56
RTX 2080 TiRTX 2080RTX 2070RTX 2060
Architecture (GPU)
NaviVega 20
Vega 10
Vega 10TU102TU104TU106TU106
Shaders
?384014083584
4352294423041920
Texture Units
?
240256224
272184144120
Base Clock Rate
?1400 MHz1200 MHz1138 MHz1350 MHz1515 MHz1410 MHz1365 MHz
GPU Boost Rate
?1750 MHz1536 MHz1474 MHz
1545 MHz1710 MHz1620 MHz1680 MHz
Memory Capacity
8GB or 16GB GDDR616GB HBM28GB HBM28GB HBM2
11GB GDDR68GB GDDR6
8GB GDDR6
6GB GDDR6
Memory Clock?
2 Gbps1.89 Gbps
1.6 Gbps
14 Gbps
14 Gbps
14 Gbps
14 Gbps
Memory Bus
256-bit4096-bit2048-bit
2048-bit
352-bit256-bit256-bit
192-bit
Memory Bandwidth
?
1 TB/s483.8 GB/s409.6 GB/s
616 GB/s448 GB/s448 GB/s
336 GB/s
ROPs
?646464
88646448
L2 Cache
?4MB4MB4MB5.5MB4MB4MB3MB
TDP
250W to 300W
300W295W210W250W215W175W160W

According to Buildzoid's observations, the PCB comes equipped with an eight-phase power delivery subsystem that features Smart Power Stage (SPS) modules. Past Radeon graphics cards used SPS packages rated for 70A, so we can expect the same for Navi. The PCB showcases spacing for two 8-pin PCIe power connectors. However, it's important to take into consideration that this is a test PCB after all, so don't go running for the pitchforks just yet. Based on the design of the power delivery subsystem and the power configurations, Buildzoid estimates that Navi's TDP (thermal design power) is somewhere between 250W to 300W. Power efficiency hasn't been AMD's strong suit so let's hope the company can prove us wrong.

Credit: BaiduCredit: Baidu
The backside of the PCB doesn't reveal any noteworthy information. There's an array of pins that is presumably part of the LED indication system that dynamically changes the color of the LEDs to reflect the graphics card's load. Buildzoid also discovered a few configuration switches that may be exclusive to this engineering sample, or maybe they're for RGB lighting. No one knows at this point.

Lastly, the PCB and hole layout implies that this particular Navi graphics card will come with a reference blower design. Reference blowers don't always have the best reputation when it comes to cooling, but they work competently as long as the graphics card has a modest TDP. Display outputs include one HDMI port and two DisplayPort. It looks like AMD might be following in Nvidia's footsteps as there appears to be a USB-C port for virtual reality headsets.