The heated discussion around the topic between CISC and RISC has never reach into a consensus, but the reality in industry turns out to be that RISC architecture processors, like ARM, PPC, etc, are seldom used as CPU in modern desktops, laptops and computation-intensive servers. They are used more on embedded computing side like phones, tablets and other mobile devices. At most recent CES 2015, ARM does not even appear there. The trend is really like that Intel with its CISC or more-CISC-less-RISC combination chip dominates the high-end processor industry with outstanding performance, whereas RISC processors are more characterized by their low power consumption targeting embedded devices.
I would just like to know without historical and commercial reasons as well as the great effort and concentration put by Intel to push CISC forward, will RISC outperforms CISC? Or maybe in future? Especially considering that CMOS fabrication hardware complexity is approaching its limit, and more parallelism is demanded for nowadays computing, which matches the superb advantages of RISC in pipelining instructions. Besides, I would like to know if there is inherent limitation of RISC that makes it not able to compete with CISC architecture in performance?
Different thoughts are appreciated. Thanks!
This is a very opinion-based topic. You should read this paper. It takes a stab at comparing RISC vs CISC in the modern world. In general it is very hard to make any solid technical argument in this area because a lot of current trends are dependent on so many factors which are irrelevant of the ISA - such as microarchitecture, circuit design, process technology, tools etc. Plus modern day ISAs are somewhat a combination of RISC and CISC. Under the hood most of the features are blended together. For instance, x86 instruction in the decoder pipeline are broken down into many much simpler RISC-like instructions. But if you look at the more recent ARM chips, they actually do something very similar. Also, ARM instructions nowadays are much more complex than they used to be back in day, and also more sophisticated than more traditional MIPS instructions. In order to make a reasonable comparison about which one is inherently better, you would have to normalize all of the other factors, which is really hard to do.