NVIDIA is discontinuing shipments of the Jetson TK1 development kit effective at the end of April, 2018.
NVIDIA's Jetson TX1 and TX2 are the newest generation of Jetson development kits. The Jetson TX1 features a 64 bit Cortex-A57 versus the 32 bit Cortex-A15 featured on the TK1. The Cortex-A57 fetches, decodes and dispatches three instructions per clock cycle and can do so out of program order, whereas the TK1 can execute 2 instructions in program order. The TX1's processor architecture allows for faster memory bandwidth and more performant memory caches as well.
The Jetson TX2 offers double the performance and efficiency for more complex AI, deep learning, and neural network applications with its integrated 256-core NVIDIA Pascal GPU and hex-core ARMv8 64-bit CPU complex, plus 8 gigs of memory.
See the NVIDIA TX1 module and development kit
See the NVIDIA TX2 module and development kit