Not just the hardware but the software too, from assembly to more abstracted languages, device drivers, user interfaces, communications links, networks, human interfaces and many more.
We have even implemented microprocessor blocks in FPGAs, writing the hardware description language and synthesising the gate level logic as well as writing the embedded software that it runs.
More recently we are working with platforms capable of running machine learning and AI. These systems are capable of running as servers for big data processing or as local Edge AI in IoT type systems.
None of the processors are of any use if they cannot communicate with the outside world via peripherals. We have a deep understanding of peripherals and have designed and consulted for some very well-known semiconductor manufacturers in this area.