Because some of those GPUs are older BATCH chips. And due to price fluctuation, demand, economy, and current inventory of these memory chips, some GPU vendors/AIBs used whatever was better/feasible or economical for them at that time.
Also, just in case you are wondering how much is the performance between both these memory modules/types is, it is minuscule. The GDDR6X variant is just 3% faster than the GDDR6 model, at least in gaming. Synthetic benchmarks might show a slight improvement though, but in games it's not very huge.
The increased raw bandwidth sometimes helps, but in many reviews the performance between the G6X and G6 variant was not VERY high. Not sure about other third-party reviews, as I'm not up to date with this, so maybe in some other reviews the performance might be slightly higher, at least on higher resolution.
NVIDIA GeForce RTX 3060 Ti with GDDR6X memory has been tested Polish techsite ITHardware obtained the first RTX 3060 Ti graphics card equipped with GDDR6X memory for their test. As a reminder, NVIDIA launched an updated version of their RTX 3060 Ti model in October last year. However, until...
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