Star Ratings for Appliances

Most folks buying electronic appliances in India would know about the energy savings guide sticker which is placed on the appliances. It’s a 5-star rating, with 5 being considered the most energy-efficient one. These ratings are standardised in India by BEE(Bureau of Energy Efficiency) under the Ministry of Power. When you dig deep into the standards for each major appliance out there, you will find that there is a fixed set of rules for testing these appliances. The sticker actually shows different things for different devices. For example, for a TV, it would be in terms of the number of “Annual Energy Consumption” which is defined by the power consumption in kWh if you were running the TV on for 6hrs/day and it’s on standby for 12hrs a day (Rest of the time considered OFF). Similarly, for a fridge, it would be annual consumption with it being ON always.

Whereas for a water heater, it’s measured in terms of standing power loss. It means how many units in kWh is consumed by your heater if you left it ON for a full day without you letting water out from the pipe(Meaning in steady-state condition). For example, if after the test, the energy consumption is below 0.32kWh for 24hrs(For a 6L Geyser), you will get 5stars. Values are pretty low, so don’t panic that your electric bill is going to skyrocket if you accidentally forgot to turn off a geyser in your bathroom. 🙂

For readers who are interested to read up on this, do check out the beestarlabel website. It contains a massive database of all registered appliances in India with their rating points and it contains tons of info on the tests that are performed and what standards are applicable. It’s one of the better-maintained govt websites out there. You can potentially learn a lot, so that next time you see one of those labels when you go shopping, you would know exactly what to make out of it.

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CoreMark: Benchmarking Processors

Developed by a non-profit, Embedded Microprocessor Benchmark Consortium(EEMBC) in 1997 is currently one of the most popular benchmarking software available to characterize and compare the processing capabilities of your embedded microcontrollers. It’s a piece of code that runs on practically any processor/controller out there and does a bunch of tests and reports the result in a standard format. The code conducts a bunch of integer arithmetic calculations, matrix manipulations, linked lists and state machine operations. So it does a few of the performance benchmarks which are used in real life (but it’s still synthetic testing though). CoreMark when it was released, was an alternative to another standard known as Dhrystone that was created back in the 1980s. The issue with Dhrystone was that you can always tweak certain settings to get a higher rating based on compiler optimisations.

CoreMark prevents compiler hacks and smart programming tricks to drive up the ratings. The tests and code are available for free on GitHub if you want to run them on any controller of your choice.

Why does this matter for an embedded developer? When you are searching for a new microcontroller for a project you can always look at the CoreMark numbers and make an informed decision(Usually the higher the better). Most good chip manufacturers give the CoreMark ratings on their products but each might give it in a slightly different manner. There are 3 key numbers you need to keep in mind for that. A single CoreMark number shows the overall performance of the chip. Then there is CoreMark/MHz which normalises the core performance based on the clock speed. A chip having a lower CoreMark/MHz can have an overall better compute capability if it’s run at a higher clock speed. The third is CoreMark/mA which gives you a flavour of energy efficiency/power consumption of your processor. So keep all of these in mind when comparing microcontrollers.

CoreMark scores submitted by users all around can be found at https://www.eembc.org/coremark/scores.php.

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