Uncovering the mystery of how the 12-inch MacBook combines long battery life with thinness

Apple has packed all of their latest laptop technology into this ultra-thin new MacBook. Some might say that Apple laptops with a battery life of nine hours are nothing new, but the amazing thing is that the new MacBook battery is only half the size of the MacBook Pro, but it can last almost the same amount of time.

The new MacBook uses a 39.7 watt-hour battery, which is 35 watt-hours smaller than the 74.9 watt-hour battery on the MacBook Pro. The 13-inch MacBook Air uses a 54 watt-hour battery, which is also larger than the new MacBook's battery.

You may be curious about how Apple achieves such high efficiency. Behind this is a combination of multiple new technologies. Three aspects contribute the most to energy saving: the new retina screen, ultra-low power memory and Intel's fifth-generation processor.

Upgraded retina display

Although I haven't measured it strictly, the retina screen is probably the most power-consuming electronic component on this laptop. The ultra-high resolution itself consumes a lot of power, and the graphics card also needs more energy to drive those millions of pixels. Because the pixels are densely arranged, the screen must also use a stronger backlight to illuminate.

Generally speaking, a stronger backlight means a larger battery is needed, just like the third-generation iPad and the second-generation iPad mini increased their battery capacity when they were upgraded to retina screens, which made the body thicker.

In a TFT-LCD screen, each pixel is partially covered by a transistor circuit that controls the red, green, and blue sub-pixels. The uncovered portion is called the pixel opening, and the opening area depends on the type and design of the panel. As the pixel opening becomes smaller, a stronger backlight is required to achieve the same level of brightness, resulting in more energy consumption.

Fortunately, there are many ways to make the opening larger. One way is to change the material of the transistor. For example, the "low temperature polycrystalline silicon panel" (LTPS-based panel) used in the iPhone 6 and iPhone 6 Plus can enhance the mobility of electrons and make the transistor smaller, so that the pixel opening area is correspondingly increased.

Another way is to redesign the pixel, which is the most likely approach for the new MacBook. Apple didn't say much about what they did to improve the pixel, but according to an animation on Apple's website, they stacked one layer of circuitry in the pixel on top of another, thereby increasing the pixel opening. Apple claims that it is precisely because of the larger pixel opening that the backlight of the new MacBook is 30% more energy-efficient than their other series of notebooks, which greatly reduces the power requirements of the display.

Core M processor

In addition to the display, the processor is also a big power consumer. The new MacBook uses Intel Broadwell Core M ultra-low voltage processor. Broadwell represents the upgrade of the process from 22 nanometers of the previous generation Haswell to 14 nanometers, which means that the size of each transistor is smaller, allowing more transistors to be loaded into the chip and improving processing efficiency. Intel claims that the Broadwell processor saves about 30% of energy consumption compared to the previous generation Haswell while ensuring the same or better performance.

However, Apple did not use the regular Core i series in the new MacBook, but used the Core M, which consumes less energy. The Core i5 in the MacBook Air requires 15 watts to work, while the Core M only needs 5 watts. The low-power processor also generates much less heat, which allows the new MacBook to be fanless, which is also an energy consumption point.

More energy-efficient memory

The new MacBook is likely to use ultra-low power memory LPDDR3, which was originally designed for smartphones and tablets. The first time LPDDR3 appeared in a MacBook series notebook was in the 2013 MacBook Air.

Generally, notebooks use DDR3L, which is the low-voltage version of DDR3. DDR3L and LPDDR3 are different in terms of architecture. Whether in operation or standby, DDR3L consumes 85% of the energy of desktop DDR3 memory. LPDDR3 only consumes 70% of the energy of desktop DDR3 when in operation, and this figure even drops to 10% in standby mode. From this point of view, the excellent energy-saving performance of LPDDR3 is obvious.

Other factors

The new MacBook's long battery life does not only depend on the above three factors.

For example, the 802.11ac version of Wi-Fi in a laptop can complete network requests more quickly, allowing the radio waves to quickly fall back to a low-power standby state. In fact, in LTE networks, smartphones also use the same concept to reduce their own power consumption.

The new MacBook's keyboard backlight is more energy efficient than the old one, which used a single set of LEDs with a layer of plastic to diffuse the light. The new keyboard has an individual LED under each key, which allows for a higher level of power control, such as more detailed brightness levels and automatic brightness adjustment for each key based on its importance.

As a winner of Toutiao's Qingyun Plan and Baijiahao's Bai+ Plan, the 2019 Baidu Digital Author of the Year, the Baijiahao's Most Popular Author in the Technology Field, the 2019 Sogou Technology and Culture Author, and the 2021 Baijiahao Quarterly Influential Creator, he has won many awards, including the 2013 Sohu Best Industry Media Person, the 2015 China New Media Entrepreneurship Competition Beijing Third Place, the 2015 Guangmang Experience Award, the 2015 China New Media Entrepreneurship Competition Finals Third Place, and the 2018 Baidu Dynamic Annual Powerful Celebrity.