RISC-V has become a big hit. There is no doubt that it has an infinitely bright future and a boundless future. However, I think it has a lot of room for improvement. This article will lead everyone to take a look at some of the current flaws in RISC-V...
Translator | Crescent Moon Editor | Zhang Wen
Exhibit | CSDN (ID: CSDNnews)
In terms of hardware design, a design that people often tout is RISC-V, whose ISA is open and does not require licensing fees. Many organizations are willing to fully support RISC-V, and the open source community is very confident in it. However, with the recent acquisition of ARM by Nvidia, people are beginning to worry. However, I think these expectations are a bit misleading, because the openness of RISC-V does not bring much benefit to users. In fact, it is the CPU manufacturer that benefits.
1. License fee
One of the biggest advantages of RISC-V is that there is no need to pay any licensing fees. Although you need to pay implementation fees to companies like SiFive, these fees are design fees, not ISA abstract implementation fees. Openness means that small chips used in washing machines and other equipment can have greater profit margins, because manufacturers do not need to pay any fees for ARM or Synopsis. Although the cost savings may benefit consumers, the openness of ISA is of little use to users for such a ROM that can only be programmed once.
2. ISA fragmentation
RISC-V intentionally defines a small ISA with extensions. Although many larger implementations will implement a common set of extensions, even the basic functions are placed in the extensions, which will make it more difficult to guarantee compatibility when publishing software in binary form. In addition, RISC-V clearly encourages manufacturers to implement custom instructions on dedicated chips, which is very good for embedded systems, but not good news for general-purpose computers and operating systems running on computers.
3. Ecological environment
RISC-V is actively promoting embedded, and this kind of move is reasonable. But many touts about RISC-V hope that it can become the main force of personal computers or servers. However, this is unlikely to be achieved, because the embedded ecological environment is completely different. ISA is not so important in embedded programming (although code reusability is important, it is not as important as general-purpose processors because it does not need to run arbitrary binary files), users and enterprises care about binary compatibility Computing at the level of performance (to avoid the waste of existing programs) and most RISC-V implementations have not yet achieved performance improvements, such as superscalar execution.
4. Openness does not pass
The opening of ISA does not have much impact on implementation. The authorization of RISC-V completely allows private design, and considering the dominance of RISC-V in embedded systems, this kind of privateness will be very common. Therefore, openness will not affect users (to control root trust), because users have no influence on the fab.
5. Design flaws
Since 1991, RISC-V has not made any progress in CPU design, and even some basic errors such as addressing mode errors have occurred. However, despite these shortcomings, it still occupies a dominant position in embedded.
In general, RISC-V will bring a revolution to academic projects and embedded development that hope to save money, but it is unlikely to affect users and developers. (Transferred from CSDN)
Reference link: https://sporks.space/2021/02/01/risc-v-isnt-as-interesting-as-you-think/
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