Need to know what volatile and non-volatile memory is resident on the Jetson TX1 and its size.
For non-volatile memory, also need to know if it is user accessible or not.
Are you speaking of RAM and hard disk? RAM is 4GB, eMMC is 16GB. Actual root partition available capacity will be less due to partitioning, total available size of a root partition with nothing in it would be approximately 14 to 15GB.
The flash utility gives you complete control over what goes in eMMC, but if you want a running system you mostly can change only the root partition (other hidden partitions are part of the boot process).
As to which part of RAM is available Linux always segregates a certain amount of RAM for kernel use, the rest can be used for user space…I think 1GB is reserved for kernel (there are kernel options which have a limited ability to modify this, I’ve not used them before). GPU does not have separate memory so anything CUDA/GPU/user land shares the rest.
Correction Note: The 3G/1G memory split applies only in 32-bit arm (the Tegra K1), and not to 64-bit (Tegra X1 does not care about this, so no kernel option for it exists there).