# How to calculate the theoretical memory bandwidth?

Hi, everyone. In NVIDIA turing architecture whitepaper, the theoretical memory bandwidth is calculated as Memory interface * Memory Clock rate / 8 (GB/s). But in an old doc, reduction.ppt in CUDA samples, it is Memory interface * Memory Clock rate * 2 / 8 (GB/s). Which one should be adopted?

It’s going to depend on how the memory clock rate is indicated/specified. Specifically, its going to depend on how the memory clock rate translates to transfers per second. There is not one single answer.

Do you means that the given memory clock rate is a theoretical peak value and the actual memory clock rate varies during data transfer? Since Memory interface * Memory Clock rate is doubled in reduction.ppt, does NVIDIA GPUs support simultaneous bidirectional data transfer for now?

No, I don’t mean any of those things. None of those things are true.

The peak theoretical memory bandwidth is transfers/second * bits/transfer * 1byte/8bits

Note that memory clock rate doesn’t appear in the above formula.

Depending on what source you are using for memory clock rate, you will have to determine how that relates to transfers/second.

But according to NVIDIA turing architecture whitepaper, Memory Bandwidth (GB/sec) is Memory Interface * Memory Clock (Data Rate) / 8 bits. Given that Memory Interface is 352 bit and Memory Clock (Data Rate) is 11 Gbps for GTX 1080Ti, Can Memory Bandwidth of 484 GB/sec be treated as its theoretical memory bandwidth?

What do you mean the source for memory clock rate?

And if I responded to that, suggesting that is correct, you would immediately point out the example from the reduction paper, which you already pointed out.

I’m not going to go back and forth on this. Both are correct. There isn’t just one formula that applies to every case, for every situation. If you want to come up with one formula, I personally would do exactly what I already suggested. Create a formula that is based on transfers per second. Then for each situation you come across, see what relationship memory clock rate must have to transfers per second, in order to make that single equation correct.

The peak theoretical memory bandwidth of GTX 1080Ti is published: