Many of the best known IP cores are soft microprocessor designs. Their instruction sets vary from small 8-bit processors, such as the 8051 and PIC, to 32-bit and 64-bit processors such as the ARM architectures or RISC-V architectures. Such processors form the "brains" of many embedded systems. They are usually RISC instruction sets rather than CISC instruction sets like x86 because less logic is required. Therefore, designs are smaller. Further, x86 leaders Intel and AMD heavily protect their processor designs' intellectual property and don't use this business model for their x86-64 lines of microprocessors.