Why RISC Five?

The Genius of RISC-V Microprocessors is a highly technical presentation of RISC-V processors, so I am breaking it down into some key issues.

While there are many ways to implement a CPU or Central Processing Unit, the two main styles are:

1. CISC or Complex Instruction Set Computer
2. RISC or Reduced Instruction Set Computer

CISC

Is the the more traditional way to design a CPU, where the instructions are more complex, where generally more work is performed for each instruction.

In olden times, it was easier for programmers to write programs with more powerful CPU instructions, and over time, CPU designers made increasingly more powerful instructions to appease programmers.

However, it requires more transistors to create more powerful instructions, more complexity, more time to decode and execute, and more energy consumed to make all this complexity work.

AMD and Intel are famous for making x86 CISC CPUs.

RISC

Is the new-fangled way to design a CPU, where the instructions are less complex, where generally less work is performed for each instruction.

In less olden times, programmers no longer write low-level machine code or assembler instructions; they use high-level compilers that make it easier to write high-level code that is translated into low-level machine code. Consequently, CPU designers no longer need to appease programmers this way.

Both theory and practice demonstrate that simpler instructions require fewer transistors to implement, less time to decode, and consume less energy. Consequently, we find RISC CPUs in products like mobile phones and other devices, where batteries put serious limits on how much energy is available for CPUs.

Apple and Qualcomm are famous for making modern RISC processors like ARM (Advanced RISC Machine), but IBM, Motorola, Sun Microsystems, and others have been making RISC processors for the other advantages of RISC.

RISC-V

Is the new kid on the block of RISC design with some interesting and innovative characteristics:

• It is 'Open Source,' so no one needs to pay companies like ARM or Intel licensing fees to use their designs. This can help lower costs.
• RISC-V has even fewer basic instructions than ARM, meaning it is possible to build RISC-V CPUs with even fewer transistors. This can help lower costs.
• In the Internet of Things (IoT), costs and energy use can be even more minimal for very small devices, such as light switches, than for ARM or other designs.
• However, being the new kid on the block, the actual performance of RISC-V lags that of ARM, but there are no technical reasons why it cannot catch up. Also, for IoT, cost is a more important consideration than performance.
• RISC-V is scalable; more instructions can be added, which means it can be implemented with performance comparable to ARM and other architectures, possibly even better.

Internet of Things

The idea is that almost any product can have a CPU and be connected to the internet. With home automation or the 'Smart Home,' we will see multifarious devices such as light switches, thermostats, sensors, refrigerators, toasters, etc., that have a CPU performing some task, the most important task being connected and communicating on the internet.

Conventional processors, such as ARM, will find it harder to compete in this market in terms of cost.

However, as ARM proved they can compete with CISC in laptops, desktops, workstations, supercomputers, and the cloud, we can expect RISC-V to attempt to compete in these spaces.

RISC-V is already competing in the supercomputer space because, for very specialized computing, fewer transistors are needed, which also means that more CPU cores can be implemented with the same number of transistors as conventional designs.