First, let's start with the first word of the name. RISC is officially interpreted as a reduced instruction set computer, with the same instruction format and the same instruction cycle of all instructions, and pipeline technology can be adopted. Many early RISC designs have a bad shortcoming-branch delay slot, which refers to the instruction space after jump or branch instruction. Instructions in space will be executed (or the branch effect will be delayed) regardless of whether the branch occurs or not. These instructions make the arithmetic and logic unit of CPU spend more time than usual to perform transmission. Nowadays, the transfer delay slot is considered as a side effect of implementing a specific RISC design, and modern RISC designs usually avoid this problem (such as PowerPC, the latest SPARC version, MIPS).
RISC-V (pronounced RISC-FIVE) instruction set is an open instruction set architecture (ISA) based on the principle of reduced instruction set computing (RISC). RISC-V is a brand-new instruction based on instruction set. RISC-V instruction set is completely open source, simple in design, easy to transplant to Unix system, modular in design, complete in tool chain, with a large number of open source implementations and streaming cases, which has been strongly supported in the community. Its advantages are completely open source, simple architecture, easy transplantation of Linux and Unix, modular design and complete tool chain.
Based on the above analysis, why do we hear so many kinds of RISC-V in a short time? This is because RISC-V, as a brand-new chip architecture, has opened up a lot of possibilities for China to independently design and manufacture CPU. The monopoly of ARM and Intel x86 on microprocessor architecture will probably be broken by the appearance of RISC-V. Some people say that RISC-V has given China a chance, and it won't be bad for everyone to start over in China. In my opinion, opportunity is a real opportunity before us, and we have no reason to waste it. Major domestic companies have long been eyeing RISC-V, and Huami Technology has also released Huangshan No.1 chip based on RISC-V. However, we should not be too optimistic. It's true to start over, but there is a gap in technology and ip research and development between China's current chip manufacturing and Europe and America. The core of domestic mainstream microprocessors is still based on the technology of these big companies. Moreover, overseas companies seize too many intellectual property rights and patents, which will make us sweat more on the road of chip manufacturing.