RISC versus CISC

The old discussion about RISC versus CISC suddenly became on the agenda again after my article about AVR to ARM.

Anders from IAR systems and a few others have contacted me to say that to call ARM a CISC was not correct. There is no doubt about that, ARM is a RISC, not a CISC processor. Advanced Risc Machines develops RISC processors.

In my article I referred to the beginning of the ARM and the beginning of AVR. The first ARM device we used was one of the first ARM 7 based architectures. This architecture had a Von Neumann bus structure, which means that there is one shared bus for program code, data and I/O. Most processor architects would say that RISC processors should have a Harvard architecture where there are separate busses for the different memories. This was implemented in the ARM 9 and it almost doubled the performance of the core. There are also CISC processors utilizing the Harvard architecture so I guess the border between CISC and RISC will never be 100% clear. However, my previous article should have been written differently. My bad.

Many people think that RISC means reduced number of instructions. Reduced in the RISC term refers to the complexity of the instructions. A RISC processor has an instruction set where every instruction is executed mostly in one clock cycle and hereby becomes very efficient in terms of execution speed. However, this requires different hardware support because it can be viewed more like “parallel processing” versus a CISC that has complex instructions and some instructions have small state machines that use multiple. For example the multiply instruction take one clock cycle in AVR and 48 in the original C51 core.

When we designed the AVR we actually added a lot of instructions to avoid having every instruction too flexible. By adding more instruction we could keep them simple and very efficient. By working with IAR systems on the C-compiler we also ended up with a very code efficient machine.

For embedded processors used in control application it is also very important to have a processor that can handle single bits in registers, memory and I/O very efficient. It is interesting to note that the C51 designed by Intel in 1980 had bit level “boolean logic” operations. These operations can be used on internal registers and a dedicated portion of the RAM memory. A similar functionality was also implemented in the AVR to make it extremely efficient for control applications. The original AVR architecture before it became Atmel was designed to do very efficient descrambling of bit streams sent to digital TV sets.

The next level of efficiency for embedded application is what the I/O Communicates without the CPU involved. This was implemented in the XMEGA AVR and an even more efficient system is implemented in the EFM32 from Energy Micro. The EFM32 has a so-called Reflex system where peripherals can be programmed to wake up each other and pass data along as needed. This is mostly implemented to utilize the low power modes of the EFM32, and will also improve the performance of the system.

Interviews and pictures from Silicon Labs and Energy Micro !

We recorded a lot of material yesterday and today and I will share some of the interviews with you soon. I am just uploading a ton of data from my various data cards. Then I need to do some edits and get it out to you. Probably in a week or two!

Here is the video of the signing. This is the same as the video on the Energy Micro blog.

This could not have been successful witout great support from professional investors. Thanks for your help over the years !

Silabs to blog-7027

Over from Left: Torleif Ahlsand (Nortzone), Tyson Tuttle (Silicon Labs), Geir Førre (Energy Micro), Steinar Fossen (Investinor).

Geir Førre informed the rest of Energy Micro at 10 am today. A few hours later they all went to a secret place to plan the next months and years. What a team !

Silabs to blog-7093

Over: Geir Førre explains to the team why he decided to sell the company

After a short introduction, Tyson Tuttle entered the room and I think all the people felt very welcome to Silicon Labs !

Silabs to blog-7103

Over: Tyson Tuttle welcome the Energy Micro team to Silicon Labs.

Øyvind Janbu and Torkel Brunsvik were singing a new song they made for this happening as well. I do have the raw material so there is not much they can do to stop me from publishing it !

Alf Bogen

Silicon Labs Acquires Energy Micro

Big news!

It is a great day at Energy Micro and Silicon Labs today!

The CEO of Energy Micro Geir Førre and the CEO of Silicon Labs Tyson Tuttle signed an agreement where Silicon Labs acquires Energy Micro. The deal is expected to close around July 1st. (the story continues after the picture)

tyson geir

This is a very strategic and interesting acquisition that I think will have a lot of positive synergies for the embedded designers worldwide. We have been working with this for several months now and I get more and more exited about what we can do together.

Silicon labs is a great company with extremely talented people. Their mixed signal expertise is second to none and they design things other people give up. What I found very interesting is their history around complex mixed signal devices like the TV and radio tuners as well as their very advanced timing devices used as reference clocks in high-end communication products. If you look at these chips you will see that they are not easy to develop. They also have a profitable microcontroller business that they now want to accelerate through this acquisition.

During this process I have met a lot of the people from Silicon Labs including the management team and founders of the company. I am really impressed about their visionary view and drive to achieve results.  I have met very humble people, yet with very aggressive goals for them selves and the company.

Energy Micro has an amazing technology and traction in the market. Our brand position and design win rate is nothing less then outstanding. It is clear to me that the curious and innovative culture is an important factor to this. This market position and culture were probably the main reasons I left Atmel and joined Energy Micro a few months back. These where probably also the main reasons Silicon labs wanted to acquire the company.

I will get back to this soon, but now I need to get all the release material for the company ready to go live soon!

We do have a lot of video from the event as well so stay tuned !

Do not hesitate to send me questions or comments on E-mail.

Thanks for reading.

Alf-Egil Bogen

CMO, Energy Micro

a.bogen@energymicro.com