According to the data, the AMD Radeon RX 7900 XT graphics card can deliver more than 7 TB per second of bandwidth. While the discussion is classified as speculative or theoretical, in this case, it is no less than a fascinating insight into AMD’s new graphics card.

In the post, the Bright Iron user does his calculations using the information found in AMD’s RDNA 3 Navi 31 flagship GPU, which offers 6 MCDs and up to 384 MB of Infinity Cache in a 3D V-Cache package.

His theory is based on information already available, such as the AMD Radeon RX 6950 XT, which is the best performer in the company’s current GPU lineup, offering 16 GB of GDDR6 memory with the help of a graphics card clocked at 18 Gbps 256-bit bus. This combination of technologies results in a bandwidth speed of 576 GB/s.

Bright Iron goes on to discuss bandwidth dwarfed by NVIDIA’s GeForce RTX 3090 GPU, which offers 936 GB/s, compared to 1,008 GB/s for the company’s RTX 3090 Ti.

Bright Iron went on to explain that AMD’s bandwidth performance is quite impressive compared to NVIDIA because of the company’s use of Infinity Cache technology. Infinity Cache is a memory that is separate from the main memory located on the AMD GPU. It is typically small in size compared to the main memory on the graphics card, but due to its proximity to the chip, Infinity Cache can be pulled at a higher rate.

MD Infinity Cache provides up to 128 MB of memory capacity and 2 TB/s of memory bandwidth. The AMD Radeon RX 6850 XT offers 512 GB/s of bandwidth as standard until you add 128 MB of Infinity Cache, increasing the bandwidth by another 1,281 GB/s and providing users with a total of 1,793 GB/s of bandwidth, far more than NVIDIA can currently produce.

The newer RDNA 3 architecture will allow Infinity Cache to reach 384 MB, which is three times higher than the previous RDNA 2 architecture. The chip can generate 192 MB from the standard Cache while utilizing another 192 MB of 3D V-Cache packaging to achieve 384 MB for the entire Infinity Cache.

Bright Iron has calculated that this new amount of Infinity Cache will yield three times the bandwidth (excluding the main memory bandwidth) assuming it runs at the same speed as RDNA 2. RDNA 2’s 128MB Infinity Cache has a maximum bandwidth of 2 TB/s (terabytes per second), so we see that RDNA 3’s 384MB is 6 TB/s.

However, it could potentially run much faster, so 6 TB/s is probably the minimum requirement; again, this does not include the additional bandwidth of main memory, which is claimed to be 24GB of GDDR6 and a 384-bit bus (don’t confuse this number with 384MB of Infinity Cache).

Memory @ 16Gbps = 16,000,000,000 bps (bits per second)

16,000,000,000 bps x 384 = 6,144,000,000,000 bps

6,144,000,000,000 bps ÷ 8 bits = 768,000,000,000 Bps (Bytes per second)

768,000,000,000 Bps ÷ 1,000,000,000,000 bytes = 0.768 TB/s

0.768 TB/s + 6 TB/s = 6.768 TB/s

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On that note, the AMD Navi 31 GPU is confirmed to feature an advanced chip packaging design with next-generation Infinity Cache. Based on @Kepler_L2 digging through AMD’s drivers for various patches and logs, it looks like the Navi 31 GPU will have as many as 6 MCDs (Multi-Cache Chips).

Each MCD is said to have up to 32MB of standard cache, and will also be available in 3D V-Cache form. This brings the standard cache to at least 256MB, while the variant with 3D V-Cache can reach 384MB Infinity Cache. Infinity Cache is also 32MB in size, half the size of the Zen 3 3D V-Cache part (64MB), but with six MCDs available, the chip could theoretically provide an additional 256MB of Infinity Cache via 3D package to provide an additional 256MB of Infinity Cache, but it looks like only half of the MCDs will be integrated onto them via 3D stacking. Thus, 256MB is standard plus 128MB of 3D V-Cache, for a total of 384MB of Infinity Cache.

This is a 3X increase over AMD’s RDNA 2 flagship Navi 21, which has only 128 MB of total Infinity Cache. The Infinity Cache architecture helps AMD pump more bandwidth to the GPU, which allows it to eliminate memory bottlenecks and provide fast caching close to the GPU, rather than through VRAM.

AMD Navi 31 GPU, the flagship RDNA 3 chip will power next-generation enthusiast cards such as the Radeon RX 7900 XT graphics card. We’ve heard that AMD is dropping the CU (compute unit) in favor of the WGP (workgroup processor) on its next-generation RDNA 3 GPU. Each WGP will house dual CUs (compute units), but with twice as many SIMD32 clusters, compared to the RDNA 2’s 2 clusters per CU.

According to the latest information, the AMD Navi 31 GPU with the RDNA 3 architecture is expected to offer a single graphics computing chip with 48 WGPs, 12 SAs and 6 SEs. This will provide a total of 12,288 stream processors, which is lower than the previous number. This will also reduce overall computing performance unless AMD goes crazy with clock frequencies over 3.0GHz on its flagship part. Navi 31 GPU will also carry 6 graphics compute chips that will have 32MB Infinity Cache each and may also carry a 64-bit (32-bit x 2) memory controller that will provide a 384-bit bus interface to the chips.

As for clock speeds, AMD Navi 31 GPUs are said to be capable of clock speeds of 3 GHz and beyond. rival Nvidia’s flagship GPUs also offer clock speeds close to 2.8 GHz, but AMD has had a significant advantage over Nvidia in clock speeds over the past generation, so this is all expected to continue. 3 GHz clock speeds mean we can expect the latest flagship product with FP32 performance in excess of 75 TFLOPs, which would be a 2.3x increase over the current RDNA 2 flagship, the RX 6950 XT.

Of course, this will bring higher power consumption, and AMD seems to have confirmed this with their next-generation graphics lineup, considering that the AMD Radeon RX 6950 XT already has a TBP of 335W, so in order to get a >2x performance increase, we can expect the Radeon RX 7900 XT to end up with a TBP closer to 400- 450W. As AMD itself has confirmed, these cards are expected to be launched later this year.

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