arm cortex processor cores

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Last Updated: Saturday, 28 March 2020 18:36

Published: Friday, 12 October 2018 04:52

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ARM: It was initially called Advanced Risc Machines Ltd, but later changed the name to ARM Ltd. It licenses CPU cores (cortex lineup), as well as GPU cores (mali lineup). NOTE: ARM primarily licenses processor cores, and NOT microprocessor or microcontroller. However, they also provide licences at system level and software level for companies which want to get the full pkg. It's cores can be used anywhere, although they are mostly used in microcontrollers. It licenses these designs (core license), as well as it allows companies to license it's instruction set (architectural license), so that they can build their own design any way they like. Apple and Qualcomm use architectural license from ARM to design their mobile processors. For Core licenses, companies receive ARM synthesizable core IP in verilog (i.e processor RTL). These IP are called soft IP, as they are in RTL. Synthesis and PnR are carried out by the companies getting these licenses.

ARM was formed in 1990, and introduced ARM6 processor family in 1991. It was based on ARM v4T processor architecture. Then came ARM7, which were still based on v4T, most popular of which was ARM7TDMI. ARMv5E arch was introduced with ARM9E processor families (E stands for enhanced, which added DSP inst for multimedia processing). Then came the ARM11 processor family based on v6 arch. At this time, it was decided to branch processor families into different types, based on their use profile. Also, each processor family would be based on arch most suited for that application type. This resulted in new product portfolio from ARM called cortex family of processors.These were subdivided into 3 profiles based on application usage. The 3 profiles were A, R, M (discussed later). New v7 arch was introduced for the cortex family. Each of these profiles had their own tailored arch, namely v7-A, v7-R and v7-M.

Though ARM had it's classic cores starting from 1990's, it's more popular "cortex" cores started appearing from 2004. These are the cores that you see everywhere in designs, the classic cores (ARM6, ARM7, etc) were used in older devices, and have disappeared from mass market. One reason for success of ARM cortex lineup is that they became very cheap, with some cortex M0 based microcontrollers sold for as low as 25 cents. This allowed these 32 bit cores to replace 8 and 16 bit microcontrollers. Let's talk about ARM ISA before delving into profiles and arch.