La Guerra de los Processors: CISC vs. RISC (x86 vs. ARM)

RISC vs. CISC Is the Wrong Lens for Comparing Modern x86, ARM CPUs -  ExtremeTech

If you have had a PC all your life, most likely its processor has been of x86 architecture . Or x86 / 64 if it is recent. Its manufacturers, Intel or AMD , mostly. In case you have had Apple computers, you may have worked with different processors. From the first Motorola of the 80s to the PowerPC of the 90s. If you are not that old, you will have had some than another Mac with Intel processor. And if you just bought it, you may enjoy the M1 processors, made by Apple itself. But let’s talk about CISC, RISC and ARM.

I mention Apple because their choice of processors for their computers serves to introduce this article: the war between two ways of designing a processor, CISC and RISC . In its early days, Apple opted for CISC-type processors (Motorola). Then it went to RISC with the IBM PowerPCs. Again, he went back to CISC with Intel and its x86 / 64. And, finally, it has gone back to the RISC philosophy with its own M1s, based on the ARM architecture, of the RISC type.

In this war there is no clear winner. Both have had their share of the market. In the somewhat chaotic personal computer sector, when IBM broke in with its PC , it ended up imposing the CISC trend by popularizing Intel processors. But in professional or industrial sectors, RISC was on its way. Until the smartphones and other devices that required low power consumption arrived. The RISC architecture, represented by ARM, was imposed as the most efficient option. And today practically all mobile devices have processors of this type. To the point that personal computers start to use it too. Who knows what the trend will be in a few years.

Panel control of an IBM System 360 .. Author : Wolfgang Stief (Flickr)

First processor was CISC

In an article titled UNIVAC, the computer that inspired Asimov , I spoke about the first computers. Among other things, I commented on the difficulty of defining a decade of the beginning of computing. But if we stick to computers as we think of them today, the 1950s may be a good starting point.

Back then, the first computers were created that could be used beyond scientific or military facilities. Still, they were very expensive, difficult to handle, and took up large rooms. You will have seen a photograph on the internet. Well, the way of being of those first thinking machines made the instructions that were given unique to that machine. Come on, you couldn’t use them in another.

The solution came from the hand of IBM , the blue giant. Founded in 1911, this computer company looked for a way to create compatible instructions for any computer, which would come to be compatible software. The idea was to be able to create programs in the form of simple code instructions that took up little memory , which was very expensive and scarce at the time. It would also save storage space.

The CISC architecture, acronym for Complex Instruction Set Computer , is the answer to this need. In Spanish, CISC means Computer with Complex Instruction Set. CISC-based processors, as defined by Wikipedia, “have a set of instructions that is characterized by being very broad and allowing complex operations between operands located in memory or in internal registers.” In practice, the CISC-type architecture reduced the cost and simplified the task of programming code, compiling it, executing it and storing it.

Interestingly, the acronym CISC was coined after this architecture existed, once its alternative RISC was created. The first computers of this type were the IBM System / 360s of the 60s and 70s or the DEC PDPs of the 70s to 90s. But there were more manufacturers of CISC-type processors. The one we know the most is Intel with its 8080 or x86, but we also have Motorola with its 68000 processors, Zilog with its Z8000 processors or the most recent AMD, which also manufactures x86 and x86 / 64 type processors.

Author : Michael Hicks (Flickr)

And to the war of the processors came RISC

For decades, the CISC architecture was more than enough. But at some point, again IBM considers looking for an alternative. It was called RISC, an acronym for Reduced Instruction Set Computer , that is, Computer with Reduced Instruction Set. The purpose was to design computers and other devices that could execute segmented or parallel instructions , something complicated with the CISC architecture. The result, less memory consumption and less execution time, among other more technical aspects, such as that they are cheaper to produce or generate less heat. And consequently less energy consumption .

RISC also had its representatives . For starters, IBM made its popular PowerPC processors. For its part, DEC created its DEC Alpha processors. RISC also gave rise to MIPS architectures, whose processors came from the factories of DEC, NEC, Siemens, Toshiab or Silicon Graphics, among others. And the SPARC architecture, created by Sun Microsystems also based on RISC.

The use of RISC spread to all types of computers and devices, but it was more popular in professional environments in the form of servers and computers of type mainframe , as well as in industrial or telecommunications technology . As I mentioned before, personal computing was practically monopolized by the CISC architecture and its variants.

ARM, the great success RISC

RISC’s most recent success has to do with ARM. The acronym ARM stands for Advanced RISC Machines . In Spanish, Advanced RISC Machines. ARM is a type of RISC-type CPU that was designed and created by Acorn Computers in the second half of the 1980s. Hence, initially, the A in ARM stood for Acorn. In 2016, it became the property of SoftBank and in 2020, NVIDIA became interested in it .

As a curiosity, the company responsible for ARM, Acorn Computers , has been sometimes regarded as the British Apple. Their relationship does not end here. The company that was created to manage the ARM licenses, called Advanced RISC Machines Limited , had both Acorn and Apple itself as participants. And a third, VLSI Technology. Acorn contributed its employees, VLSI its tools and technology, and Apple invested about $ 3 million. It’s more. For Apple Newton , Apple’s PDA and predecessor of the iPhone and iPad, an ARM CPU was used. Specifically, an ARM 610.

The ARM architecture is licensable. That is, any manufacturer can create ARM processors by paying a proprietary license . Unlike processors like x86. Hence much of its success. Currently, brands such as Apple, Alcatel-Lucent, Broadcom, DEC, LG, Nokia, NVIDIA, Microsoft itself, Sony, Qualcomm (the most popular for years), Samsung or Texas Instruments, manufacture their own ARM architecture CPUs to all kinds of electronic devices.

Today we find ARM processors in smartphones, tablets, smart watches and others wearables , calculators, NAS devices , routers and a long etcetera. If it is small and / or has a battery, it is very likely that it includes ARM inside. According to Statista , in 2019, 90% of mobile processors were ARM. Also 90% of processors for IoT solutions. For driving assistance and entertainment devices during the trip, ARM was in 75% of vehicles of this type.

The keys to the success of ARM are several. The first to come out in any debate in this regard is the lower power consumption of this type of processors. Something basic for devices such as smartphones that depend on a battery whose technology has barely evolved in recent decades. While there is no real alternative to current batteries, manufacturers can only reduce the rest of the elements so that they can place a larger battery in the available space.

The lower cost of production . ARM-type chips or CPUs can be manufactured by paying a license instead of buying them outright like x86 or similar. You are not dependent on purchasing them from a manufacturer, as with other processors. This is an advantage in several ways. You control the manufacturing, you can make improvements and you do not depend on a third party. Hence the Apple’s decision to design their own processors.

RISC-V processor prototype. Author : Chiara Coetzee (Flickr)

RISC-V, the pillar of free hardware

Beyond the omnipresence of ARM in certain computing and electronics markets, the RISC architecture has also gained favor with the community open source . That is, in the search for a free and open processor or CPU, the RISC architecture has been chosen as a reference. The result, the project known as RISC-V , which I talked about some time ago.

Taking inspiration from the free software movement , which has made It is possible to create programs and applications with the collaboration and enthusiasm of programmers and companies around the world, companies, public bodies and individuals have come together to make the free equivalent of hardware. That is, create an architecture that can be replicated and manufactured without paying a commercial license .

One of the reasons why RISC -V has received the attention of, for example, the European Union, it is due to the cold war that has been taking place in recent years between the United States and China as far as technology is concerned. One only has to take a look at the lists of world’s fastest supercomputers to see that with each update of that list overlapping computers made in USA and computers made in China .

Such is this competitiveness, that years ago China dispensed with US technology to create its own processors. Japan also has its own technology. But Europe, for its part, has realized that it needs its own chips. RISC-V is a first step towards your technological independence in that sense.