I've used the desktop version a few times, but the GUI is now available online. It does not allow you to compile C code to assembly, but you can run example as

I've used the desktop version a few times, but the GUI is now available online. It does not allow you to compile C code to assembly, but you can run example assembly code through the system and observer cache hits/misses, memory access and I/O accesses. It's a really useful educational tool.