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ARM or X86
 

Busting myths

 

There are preconceived ideas about the typical properties of ARM and X86 processors. A comparison of performance, heat generation and component cost tends to be an eye-opener.

- I mean that way too many customers are making the strategic choice between ARM and X86 based on opinions rather than facts on what’s best for their application, says Robert Helenius, Product Manager at Hectronic AB.  


ARM and X86 processors with similar properties are included to make the comparison relevant. They are all offering reasonably good computing performance, graphics and versatile I/O interface and are targeting applications in the embedded segment. 
 
The comparison includes iMX6 processors from Freescale (ARM Cortex A9), Intel Atom E3800 series processors (X86) and AMD Embedded G-Series SOC (X86). All three processor families offer single, dual or quad core versions.
 
- These processors are common choices in the low-end embedded segment, low-end at least from an X86 perspective, says Robert Helenius.
 
Let’s begin the comparison with performance. There are of course a number of types of processor performances such as graphics, floating point or integer calculations performance. We choose to compare PassMark data for the sake of simplicity. It will not include all aspects but gives a rough indication on CPU performance. The result is shown in the diagram below. Data were collected from the site www.cpubenchmark.net.
 
Performance comparison of three ARM Cortex A9 processors and six X86 processors from the two major manufacturers Intel and AMD. The red, dotted and two-pointed arrows point out two pairs of processors, one ARM and one X86 processor in each pair, with similar performance. The argumentation and conclusions in the text is based on these two pairs of processors.
 
The results from the PassMark tests indicate that two pairs of processors show roughly the same performance (red dotted two-pointed arrows). The dual core iMX 6 ARM processor is similar to the single core Intel Atom E3815 in this respect. The quad core iMX 6 scores close to the same as the dual core AMD GX-201HA. 
 
- In this case two ARM A9 cores are needed to obtain about the same performance level as one of these particular X86 processor cores, he says.
 
Further discussions are based on the two pairs of processors for which performance levels show similarities. What about heat generation then? The so called Thermal Design Power (TDP) is the measure of the power consumption of a processor when it’s utilized to a maximum. The power consumption is finally turned into heat in the component, heat that needs to be dissipated. Thus Thermal Design power figures are suitable data to use in a comparison of heat generated and to challenge a preconceived idea.   
 
- One of the more common myths is that an ARM processor generally generates significantly less heat than an X86 processor, says Robert Helenius.
 
The diagram below busts that myth, at least for the compared ARM and X86 processors with CPU and GPU integrated. The two pairs of processors with similar performance also have a similar TDP and consequently generate the same amount of heat stressed to their maximum.
 
Heat generated from the eight processors in the comparison. Four processors are greyed out to highlight the two pairs of processors showing similarities. The two pairs showing similar performance levels in the prior diagram also generate the same amount of heat and thereby bust the myth that ARM processors generate less heat.
 
In the performance and heat generation aspect it wouldn’t make a difference if an ARM or X86 processor was chosen from the processor options in the comparison. There are ARM alternatives and X86 options with similar performance that will generate the same heat when the processors are stressed. The result is shown in the diagram.
 
Robert Helenius aims to bust yet another general myth. Cost sensitive applications manufactured in large volumes are often believed to benefit from being based on ARM processors to reduce the Bill of Material (BOM) cost. So let’s take the comparison of our particular ARM and X86 processors one step further by involving component cost to check if that’s true in this segment.
 
The cost comparison below is based on the official (from websites) component prices from Freescale and Intel in 1k volumes. AMD has no publicly stated prices of their X86 processors so estimations based on Hectronic prices were used.
 
- The conclusion is quite simply that to obtain a particular computing performance level in your application the component cost will be similar independent of if you are using one of the ARM or an X86 processor in the comparison, he says.
 
Processor cost comparison. Performance and heat generation show significant similarities in the two pairs of processors, one ARM and one X86 processors in each pair. The above diagram shows that the component cost also is roughly the same. Four processors are greyed out to highlight the two pairs of processors showing similarities.
 
Robert Helenius means, based on the above diagrams and line of reasoning, that in this case some other aspect than processor performance, heat generation and component cost has to decide if to choose an ARM processor or an X86 ditto. He has a suggestion.
 
- Make the choice between ARM and X86 based on the preferred eco system of hardware and software, the eco system that matches the application requirements and your vertical market, he says. 
 
Traditionally ARM processors have successfully been used in battery powered and handheld units. X86 processor alternatives have occupied the market segments requiring powerful processors. Nowadays more ARM processors with increased performance and higher clock frequencies are released. At the same time X86 processors targeting compact and battery operated applications and X86 options adapted for particular vertical markets are released. 
 
ARM and X86 processors are head to head competitors in more and more performance segments and for an increasing number of applications. There are of course differences in the amount of and type of I/O provided by individual CPUs but that is a different story.     
 
Hectronic develops embedded computers based on both ARM and X86 processors. We have vast hands on experiences in pros and cons for the ARM and X86 architecture respectively. We look forward to the discussion and considerations leading to the decision on which architecture of the two to choose to best match the requirements of your application.
 

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