Just to point out, SK Hynix does indeed have 4 Gb/s HBM2e stacks which they showcased last week at ISSCC-2020 as stated in a reply to the leaker by Twitter user Hans De Vries.
so HK Hynix saying they don't have the HBM2e that can go that fast = they just showcased it at isscc-2020
so HK Hynix is Misrepresenting the truth....maybe
That's 512 GB/s for the die stack(16GB per chip here- 128/8bits=16GB) on a 1024 Bus
on a 4096 bus that would be 512GB's x4(for 4x1024) = 2 TB/s
but 12GB Vid card means 4GB sticks and 4 of them - one used for ECC so instead of 16GB you have 12 GB.... maybe
i mean you are NOT going to have 6GB HBM2E or 3GB HBM2E stacks
otherwise you use 1 chip - that means 1024 bus or 2 chips on 2048 bus - that means 8GB,16GB,24GB,32GB or 48GB
the larger the bus the better for bandwidth and more chips means more ram - and you might as well go for denser ram
they also said they were doing 12-high stack - which would be 768GB/s min per stack in a previous story - which if pushed like samsung could maybe do 1TB/s
posted Dec
For HBMe, manufacturers such as Micron, Samsung or SK Hynix simply use 2 GB dies instead of those with 1 GB, which increases the storage density per stack to 16 GB. The new high bandwidth memory with 24 GB, on the other hand, is a 12-Hi design with an I / O die and ergo twelve DRAM chips with 2 GB each. The data rate is 2.4 GBit / s per stack and thus the data transfer rate of a 3D stack on a 1,024-bit channel is around 307 GByte / s.
https://www.golem.de/news/high-bandwidth-memory-jedec-spezifiziert-stapelspeicher-mit-24-gbyte-1812-138299.html if they can achieve 512GB/s per stack then with 4 chips at you would have 2 TB/s and 96GB ram or 192GB with 8 stacks - like ampere titan
HK might be sly and say it's fake because it not in full production yet and just test production