how big is the gpu memory on this board?

When I use one 3D CNN, it works well.
But, I use two 3D CNN at the same time, does not working by insufficient memory size at first.
so, i expand swap memory to 4GB.
after then, when i running the code of two 3D CNN, the board is not working or working very slowly.
I guess that cause is insufficient GPU memory or power.

Can i solve this problem? or buy another board like tx2?

i use https://www.adafruit.com/product/1466 for power.
and the networks are 3D Resnets.

Have you kept an eye on the memory usage in tegrastats while running your application? It may be slowing down when GPU is consuming most of the 4GB memory because system memory is being paged out to accommodate the large GPU memory allocations.

If you require more GPU memory, you could upgrade to TX2 (8GB) or Xavier (16GB).