ASUS Eee Pad Transformer Prime & NVIDIA Tegra 3 Review
by Anand Lal Shimpi on December 1, 2011 1:00 AM ESTThe Three Power Profiles
There are three power profiles ASUS and NVIDIA have defined on the Prime: Normal, Balanced and Power Saver. Normal allows the CPU to run at up to 1.4GHz with only a single core active, and 1.3GHz otherwise. Balanced is the default setting and it drops maximum CPU clock to 1.2GHz and favors lower clock/voltage targets on the curve compared to Normal mode. Power Saver caps CPU frequency at 1GHz with 1 - 2 cores active, 760MHz with 3 cores active and 620MHz with 4 cores active. It's unclear what the impact is on GPU clocks/performance.
Regardless of power profile, video playback capabilities are untouched - all profiles are able to play 1080p High Profile H.264 content at up to 40Mbps.
The performance impact of these various profiles varies depending on what you're doing. I ran a mixture of CPU and GPU bound tests in all profiles to measure their impact. The results are below:
I reformatted the SunSpider and BrowserMark scores to keep the magnitude of the numbers in line with the rest in the chart, and to make higher numbers = better performance across the board. For the most part you can see that the difference between Normal and Balanced is pretty small. Numerically it works out to be a 5 - 15% gap depending on the benchmark. The latter end of the range is big enough where the performance conscious will want to stay in Normal mode, but it's possible to do without it.
It's interesting to note that the impact on GPU performance isn't that major across the board. It looks like NVIDIA is primarily modulating CPU speed here. The impact on JavaScript rendering performance is huge when you enable the Power Saving mode. In this state the Prime performs like a Tegra 2 based Gingerbread phone.
Power Profiles & Super IPS+ Toggles
Unlike (far too) many of its competitors, ASUS limits its customizations to those that are almost purely functional. ASUS is clearly aware of the fine line between useful improvements and clutter.
The most obvious customization is in the Quick Settings tool:
ASUS' implementation is far busier but it's all extremely useful. You get one tap access to Super IPS+ mode, as well as one tap switching between Power Saving, Balanced and Normal power profiles. I'm pleased to report that toggling any of these modes is pretty much instant, there's hardly any lag between when you tap a button and its impact takes effect. Response time is a particularly important as it directly impacts how frequently the tool is used. In this case I have no issues switching between power profiles because it's pretty much effortless.
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ATOmega - Tuesday, December 6, 2011 - link
Exactly my reasoning, and it's easy enough to see that the Transformer Prime boasts better features like GPS, camera and display.After having owned an iPad2, there must be a reason why I want this thing. And it's for all the things Apple decided to fleece me on so that they could jack up their margins.
I never liked Apple in the first place, but it's obvious they don't want to truly compete with the Android OS.
sigmatau - Thursday, December 1, 2011 - link
I was really hoping Nvidia would have something special with kal-el. This is pretty horrible when compared to hardware that has been available for about a year.It seems that the Nvidia-equiped tablets should be targeted at a much lower price point. They definetly should not be in the top tier tablets. I can see them selling at $300 or less.
UpSpin - Thursday, December 1, 2011 - link
Don't forget the display brightness. I don't think that the processor makes such a huge difference in power consumption, but the display on the Prime is much much brighter than the display of the iPad, and this will consume a huge amount of power. It's also brighter than the display of the first gen transformer, and the prime has a quad core and it gets the same or higher battery life than the first gen, I think that's really a big improvement.And if you want to use a tablet on the go, outside the house, you really need the brightest display possible. And as you can see in the picture, the difference between the sunlight visibility of the iPad and Prime is like day and night. Therefore I at least, sacrifice the 3 hours less battery life.
name99 - Thursday, December 1, 2011 - link
The display surely only uses more power if you drive it at a brighter level?And a well-designed tablet should have a light sensor, and should do a good job of auto-calibrating the brightness to the environment, so that most of the time it is NOT running the screen in bright mode. After all, that's what we expect regarding the core --- we throttle CPU when it's not needed. So, sorry, I don't think this is an acceptable answer.
I continue to state my original thesis --- I suspect that DRAM power is substantially more important than most people believe, and that one of Apple's advantages is that they ship iOS devices with minimal DRAM. This is obviously a hassle for developers, and even for some power users, but that's the tradeoff one has to make.
(Also what's the story with Android and VM? iOS does NOT do any "write" swapping --- code is paged in, but data is not paged out, and I expect that this is a power issue, nothing else --- Apple doesn't want the power hit of swapping.
I thought Android was like this --- did not write pages --- but I have read stuff recently that said no, it is now using standard desktop type VM, which is likely also a power sink.)
metafor - Thursday, December 1, 2011 - link
nVidia's solution is actually much more sophisticated than that. It's similar to a method Intel started using a ways back for laptops.It's not just auto-dimming the entire screen; it's auto-dimming every pixel individually. There is fine-grain control over the LED backlight of the display. Areas in each frame that contains black will now not only have the LCD crystal for that pixel in a "block" mode, but it will also have the backlight for that specific pixel dim.
This actually produces benefits other than just battery life; one of the biggest problems with LCD's is that blacks aren't really black because the crystal isn't able to block 100% of the backlight.
By dimming the backlight, the parts of an image that is supposed to be black will be closer to true black. This improves contrast and provides for more accurate pictures.
UpSpin - Friday, December 2, 2011 - link
how shall this work if the backlight is created by an LED array at the edge, which almost all smaller (<20") displays are. So with an edge lit backlight you can't reduce the LED brightness block wise.This is different if the used panel has a full array of LEDs, which is expensive, more power consuming and thicker, so a no go on a mobile device that thin. And neither Intel nor Nvidia have impact on this, because this requires a different panel.
TechAnandUser - Friday, December 2, 2011 - link
BenchMarking App's are not yet optimized. So please wait !!fteoath64 - Friday, December 2, 2011 - link
Why would you want a Win8 tablet ?. Its slow, heavy, short battery-life and probably cost 50% more!.You are better off with a mid-range slim laptop which you probably have. So unless you grab one of these or already have an ipad, you have no idea what a tablet can do for you.eddman - Friday, December 2, 2011 - link
You might have a time machine then, cause right now there are no win 8 tablets, let alone ARM based ones.tipoo - Thursday, December 15, 2011 - link
"Its slow, heavy, short battery-life and probably cost 50% more"Citation needed, citation needed, citation needed, and citation needed respectively. None of us have tested finalized W8 table hardware yet, unless you are from the future.