Here's the thing. You said "The 970 has 4GB of high speed GDDR5."

Is it in the same family? Yes. No one's arguing that.

As someone who is a engineer who studies GPUs, I am telling you, specifically, in science, no one says the 970 has 4GB. If you want to be "specific" like you said, then you shouldn't either. It's not the same thing.

If you're saying "VRAM family" you're referring to the taxonomic grouping of GPU RAM, which includes things from DDR2 to GDDR5X to HBM.

So your reasoning for saying the 970 has 4GB is because random people say "the 970 has 4GB?" Let's get system ram and cache in there, then, too.

Also, saying 3.5GB GDDR5+.5GB DDR0=4GB GDDR5 is incorrect. It's not one or the other, that's not how VRAM works. 3.5GB is equivalent to 3.5GB. But that's not what you said. You said 3.5GB is equivalent to 4GB, which is not true unless you're okay with calling .5GB DDR0, .5GB GDDR5 which means you'd say DDR0 is equal to GDDR5, too. Which you said you don't.

It's okay to just admit you're wrong, you know?