Ultrabook ULV vs Notebook Mobile CPUs

Posted on 04 January 2012, Last updated on 04 January 2012 by

P1010501A lot of people have been asking the very sensible question – Why Ultrabook when you can get a 1.5KG notebook that delivers the same battery life and runs at a higher clock rate?

Update: A follow-up test, focussing on CPU power only, has now been published.

In nearly all comparison cases, the ‘lower clocked’ Ultrabook is based on an Ultra Low Voltage (ULV) 1.3-1.8Ghz Core i3, i5 or i7 CPU and is being compared to a laptop running a standard mobile equivalent of 2.2-2.5Ghz. With Intel Turbo Boost some of the clock rates can go higher but it’s not important for the comparison.

What’s the difference?

The simple answer is that the laptops using the Mobile CPU are less efficient and takes more energy to get the same thing done as on an Ultrabook. Lower efficiency means higher temperatures, shorter battery life and as a result, the need for a bigger battery pack and a bigger fan, which can get noisy.

In order to give you some real-world figures I went out and bought a Samsung NP350 with a 2.2Ghz Core i3 Mobile CPUfor about €430 (pre-tax.) The NP350 is a VERY interesting laptop for a number of reasons that I will go into in another article (I’ve chosen the the NP350 to be my companion at CES this year) but to summarise, we’re looking at a Core i3 CPU that runs from 800Mhz  – 2200Mhz (SpeedStep. No Turbo Boost,) 4GB RAM, a 600GB hard disk drive, 12.5” screen at 1366×768 and a weight of 1.4KG. In terms of specs and performance it matches the Acer Aspire S3 very closely indeed, for nearly half the price.

In fact, if you’re looking at the Acer Aspire S3, do take a close look at the NP350. It’s NOT as efficient but because it uses lighter plastics and doesn’t focus on an ultra-thin style, Samsung have managed to put a 60Wh 47Wh battery inside a 1.4KG device. That’s 62% 27% bigger than the battery on the Acer Aspire S3. Does this mean the NP350 matches Ultrabooks in every aspect? Almost.

The NP350 swaps style for battery size but there’s an important caveat; the NP350 may have shorter battery life in some scenarios because the ‘mobile’ CPU can drain battery at a shockingly high rate when under load. In extreme cases, 40% more than the Acer Aspire S3. In average use cases, it may not be such an issue but let’s take a look to see how the Samsung NP350 with the Core i3 Mobile CPU (Core i3 2330M 800-2200Mhz) compares to the Acer Aspire S3 with the Core i5 Ultra-Low Voltage (Core i5 2467M 800-2300Mhz)

Idle Drain

To test the drain when the platform is idle I turn off Wi-Fi and sound, put the device into power-saving battery profile, wait until all disk and CPU activity has settled and run ‘perfmon’ over a few minutes to watch the drain rates. As the screen goes off I leave the device for about 20-40 seconds and then take a look at the graph for the lowest measurement figure.

The Acer Aspire S3 uses 3.0W minimum

The Samsung NP350 uses 4.0W minimum

Note that the difference here could simply be down to engineering. With the CPU’s at their lowest power states, the differences are probably due to board and component design and choice. I suspect the Samsung motherboard is more modular and uses cheaper components.

Streaming Audio

In this scenario the Wi-Fi is on, the screen is on its lowest setting and we’re streaming Groove Salad from Soma.fm

The Acer Aspire S3 uses about 8W

The Samsung NP350 uses about 7W

Interestingly the Samsung is ahead in this test. Why? The CPU is barely being used and the differences could be down to Wi-Fi modules and screen backlight. The Samsung NP350 uses an Intel Centrino Wi-Fi card which I’ve measured using just 300-400mw of power for this test. In this scenario, the Samsung NP350 would return  nearly double the battery life of the Acer Aspire S3 Correction: Based on the 47Wh battery of the NP350, it would return a battery life of about 150% of the Acer Aspire S3.

Average Web Working scenario

Using ‘balanced’power mode, with applications and web running the CPU is able to boost up, and step down based on requirements. Intel Core CPUs of all levels do an excellent job and here we see the potentially higher-power mobile chipset doing well. The NP350 runs at a lower average rate than the Acer S3

The Acer S3 operates in an average 10W of drain in the scenario.

The Samsung NP350 operates in an average 7.5W of drain in the scenario.

For people looking to run a few apps in a browser, input text and browse the web occasionally, the NP350 offers a battery life of around 8 hours. That’s DOUBLE the battery life of the Acer Aspire S3 in the same scenario, with the same CPU power and weight, and much lower cost.

Correction. The NP350 has a 47Wh battery capacity, not 60Wh as previously stated. In this scenario the NP350 runs for about 6hrs. The Acer Aspire S3 runs for about 4hrs.

Typical Office Scenario

Unfortunately I don’t have test results for the Acer Aspire in what is possibly the most likely usage scenario with a number of browser tabs open, some music playing, Skype running, Office (starter) 2010 running Word, Windows Live Writer and a couple of screen gadgets running. Total processes running: around 100.

The Samsung NP350 averages around 10W with a YouTube video playing. I’m extremely impressed with this figure as it means 6hrs nearly 5hrs of battery life although if we compare it to Samsung’s best, the 900X1B which uses the ULV equivalent at 1300Mhz, the power usage is down to under 7W. It’s a hint to what comes next as the mobile CPU starts to ramp up in power usage very quickly compared to the ULV CPU.

Video Conversion

Using Cyberlink Media Espresso I converted a 1080p video down to 480p and measured the power required.

The Samsung NP350 CPU and GPU started working hard and Tthe CPU drain ranged from 17W in battery saving mode to 36W in high-performance mode. This high-end figure blows away the 19W drain I saw on the Samsung 900X1B. Other Ultrabook platforms I’ve tested have used between 20 and 24W for this test.

This is where the mobile CPU starts to fall on its face. Under load, the power required is significantly more than the ULV equivalent for the same performance. The same effect would be seen when unzipping, spreadsheet recalculations, CPU-bound video playback, batch image editing and other CPU-heavy scenarios.

Update: I left out an important bit of information in this post. The ULV processor gets Turbo Boost up to around 2.2Ghz in this scenario and performs the render in much the same time as the mobile CPU. (2:05 for a 30Mbps 1080p to 6mbps 720p H.264) The ‘area under the watt/time curve’ is much less with the ULV CPU.

 

cinebench 11.5 cpu batt high perfHighest Drain scenario

To test the biggest load on the NP350 I ran a GPU test and a CPU test and watched the drain go up to over 43W. On the Acer Aspire S3 the maximum drain I was able to achieve was 31W.

Summary

Apart from the fact that the Samsung NP350 with Core i3 looks like a damn good value laptop, it’s clear that laptops based on mobile CPUs have the potential to drain battery much faster than a Ultrabook based on an ultra-low-voltage CPU. Not only does that mean potentially lower battery life under high CPU load scenarios, it also means that the laptops have to be designed for worst-case thermals. That means bigger fans, more air-space and heat-sink, potentially higher keyboard and back temperatures and of course, the related fan noise.

The NP350 shows that it’s possible to make a light device with a big battery to compensate but this is not always the case and the NP350 certainly doesn’t deliver the style of an Ultrabook.

Correction: The NP350 provides a battery size that is comparable with an Ultrabook – 47Wh capacity.

Ultra low voltage CPUs are, like high-performance CPUs, some of the most complex and high quality CPUs you can have in a laptop. They will cost more but they do return some significant power savings under high-load conditions and allow designers more freedom to make laptops thinner and lighter.

The question is, would you trade style for a bigger battery? The HP Folio and Samsung NP530 are two Ultrabooks that appear to be positioned in that area but i’m sure we’ll see more standard ‘laptops’ that are positioned like the NP350 as sensible, professional, high-value choices.

Update: A follow-up test, focussing on CPU power only, has now been published.

Recommended Reading

Top Ultra Mobile PCs

Dell Latitude E7440
14.0" Intel Core i5-4200U
Viliv S5
4.8" Intel Atom (Silverthorne)
Acer Aspire Switch 10
10.1" Intel Atom Z3745
Lenovo Ideapad Flex 10
10.1" Intel Celeron N2806
Acer Aspire E11 ES1
11.6" Intel Celeron N2840
Toshiba Portege Z930
13.3" Intel Core i5 3427U
GPD Win 2
6.0" Intel m3 7Y30
GPD Pocket 2
7.0" Intel Core m3-8100Y
Fujitsu Lifebook U1010
5.6" Intel A110 (Stealey)
ASUS R50A
5.6" Intel Atom