Tuesday, September 22nd 2020
The Reason Why NVIDIA's GeForce RTX 3080 GPU Uses 19 Gbps GDDR6X Memory and not Faster Variants
When NVIDIA announced its next-generation GeForce RTX 3080 and 3090 Ampere GPUs, it specified that the memory found in the new GPUs will be Micron's GDDR6X variant with 19 Gbps speed. However, being that there are faster GDDR6X modules already available in a 21 Gbps variant, everyone was left wondering why NVIDIA didn't just use the faster memory from Micron. That is exactly what Igor's Lab, a technology website, has been wondering as well. They have decided to conduct testing with an infrared camera that measures the heat produced. To check out the full testing setup and how they tested everything, you can go here and read it, including watching the video embedded.
Micron chips like GDDR5, GDDR5X, and GDDR6 are rated for the maximum junction temperature (TJ Max) of 100 degrees Celsius. It is recommended that these chips should run anywhere from 0C to 95C for the best results. However, when it comes to the new GDDR6X modules found in the new graphics cards, they are not yet any official specifications available to the public. Igor's Lab estimates that they can reach 120C before they become damaged, meaning that TJ Max should be 110C or 105C. When measuring the temperature of GDDR6X modules, Igor found out that the hottest chip ran at 104C, meaning that the chips are running pretty close to the TJ Max they are (supposedly) specified. It is NVIDIA's PCB design decisions that are leading up to this, as the hottest chips are running next to voltage regulators, which can get pretty hot on their own.
The takeaway here is that the heat produced from the card is quite huge with a TGP of 320 W, meaning that the cooling is quite a problem which NVIDIA managed to keep under control, however, the design decisions resulted in some possible performance loss. Instead of NVIDIA using Micron's faster 21 Gbps chips, they are forced to use the 19 Gbps variants. It is not like there would be supply issues as NVIDIA is Micron's only GDDR6X customer, however, the real reason is heat management. The speedup from a slower 19 Gbps chip to faster 21 Gbps chips is plus 10%, meaning that the heat output would follow the percentage, resulting in even greater TGP of the card. The conclusion drawn here is that the current chips are limited by temperature only, as the card is pretty hot, and that is why NVIDIA doesn't use the faster GDDR6X variant.
Sources:
Igor's Lab, via Tom's Hardware
Micron chips like GDDR5, GDDR5X, and GDDR6 are rated for the maximum junction temperature (TJ Max) of 100 degrees Celsius. It is recommended that these chips should run anywhere from 0C to 95C for the best results. However, when it comes to the new GDDR6X modules found in the new graphics cards, they are not yet any official specifications available to the public. Igor's Lab estimates that they can reach 120C before they become damaged, meaning that TJ Max should be 110C or 105C. When measuring the temperature of GDDR6X modules, Igor found out that the hottest chip ran at 104C, meaning that the chips are running pretty close to the TJ Max they are (supposedly) specified. It is NVIDIA's PCB design decisions that are leading up to this, as the hottest chips are running next to voltage regulators, which can get pretty hot on their own.
55 Comments on The Reason Why NVIDIA's GeForce RTX 3080 GPU Uses 19 Gbps GDDR6X Memory and not Faster Variants
With new cooling innovation that cools both VRM and memory properly enables them to use 21Gbit GDDR6X on partner cards.
What I heard there is no restrictions for partners to use the faster 21Gbit memory.
ALSO a tactic of nvidias have been to milk the the first wave of restless buyers with cut down and restricted versions of their GFX cards.
Then later release a "Super" version with 21Gbit GDDR6X or a 3080Ti with 352-bit memory bus with 22GB and 21Gbit GDDR6X.
Notice that the first wave of 3080 lacks any 20GB versions and I really don't see any reason for this other than to milk the first ware of buyers. 3080 with 20GB is needed for TRUE 4K future gaming, some 4K games already MAX out 10GB so to be able to fully enjoy future 4K games with 3080 you need 20GB.
I'll see myself out now
What I'm saying is the extra performance that could have been is not a reason not to buy a something.
Edit: probably another reason for the slower memory is the difference to GDDR6 that is in the RTX3070, the performance difference would be too high, and the performance of the RTX3080 would get too close to the performance of RTX3090.
I've already clarified as well ;)
if not, then this reason is bs and Nvidia just want to gimp RTX 3080 with memory bandwidth for segmentation purposes.
I remember some 5700XT having to sell for very low prices because they ran their memory too hot (Asus tuf and MSI evoke gen 1), and the temps were slightly under 100°C.
Although this time around the FE's pricing and thermal performance has forced AIB to lower the price on their premium models.
So it's still a bonus.