Samsung Chromebook (XE303) Review: Testing ARM's Cortex A15
by Anand Lal Shimpi on October 31, 2012 9:00 AM ESTFinal Words
The move to ARM doesn't fundamentally change the performance or usability of the Chromebook. It's still a slow (relative to more expensive notebooks), limited use notebook. That's not necessarily a bad thing, but you need to be aware of what you're getting into with this thing.
The display is functional but not very good. Build quality is decent but the new Chromebook is still a plastic notebook. Thankfully the keyboard and trackpad are both pretty decent.
For a basic web browsing and glorified typewriter platform, the Chromebook really does get the job done. It's a very focused, simple device that serves its purpose well. I don't know how big the Chromebook niche is, but Google has targeted it very well. At $249 if you need a physical keyboard and only need basic web browsing support, I don't know that there's a better solution. As an almost-disposable notebook for writing and browsing the web, I'm happy with the Chromebook. Good ultraportables are much more expensive, and even low cost PCs don't come with any sort of solid state storage. Admittedly the eMMC solution in the Chromebook isn't setting any records, but it does deliver consistent IO performance which is more than I can say for a cheap 5400 RPM 2.5" hard drive.
Ultimately the Chromebook puts pressure on the traditional PC notebook ecosystem from below. Tablets have been doing that for a while but they are a physically different form factor. For those who still want a traditional notebook form factor, there hasn't been much low-cost competition. The Chromebook applies a good amount of pressure there. Compared to a $1000 notebook, the Chromebook's display isn't great but move down into the $500 - $700 range and it doesn't look all that bad thanks to many PC makers failing to invest in good quality panels. If a $249 Chromebook delivers a competitive keyboard, trackpad, display resolution and quality experience to your $499 PC notebook, it's time for a change. With Apple pushing at the top and Google working the bottom, the hope is that the entire PC notebook stack gets better.
On the SoC side, our first look at ARM's Cortex A15 is quite positive from a performance standpoint. I'm still not convinced on its power consumption for smartphone use (big.LITTLE must exist for a reason) but from a performance standpoint, it's going to make current smartphone/tablet SoCs feel very slow. And that's something we can all look forward to in 2013.
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Krysto - Thursday, November 1, 2012 - link
Tablets and phones don't boot-up instantaneously. That's waking from idle mode that you're talking about, which basically just means turning on the screen.Krysto - Wednesday, October 31, 2012 - link
When Cortex A7 arrives in big.Little I expect the idle times to drop dramatically in A15 set-ups, and I doubt Intel can keep up with that. Not to mention they still won't keep up in graphics department.Anand, can you stop plugging Surface into Android and Chromebook reviews? Why would I want to hear how Surface might do in the future with this chip that Chromebook already has? Seriously.
Exophase - Wednesday, October 31, 2012 - link
Anand's Cortex-A15 diagram looks really weird vs an official one.. http://regmedia.co.uk/2011/10/20/arm_a15_pipeline_...Three instructions are decoded and dispatched to 5 clusters of 8 execution queues (8 slots each) per cycle, then each cycle each execution queue can issue a cycle to its associated execution unit (note this diagram is using issue/dispatch opposite from how it's often used). There's no execution relationship like given in Anand's diagram, the clusters are: NEON (2x), load/store (2x), simple ALU (2x), multiply, and branch.
Anand Lal Shimpi - Wednesday, October 31, 2012 - link
I based my diagram on a lot of the content in here:http://www.arm.com/files/pdf/AT-Exploring_the_Desi...
Slide 20 introduces the independent issue queues, although subsequent slides make it all a bit more ambiguous (and more like the block diagram you included). I didn't include "issue" width for each of the arrows in my diagram to keep thing simple but I can see that it can definitely give the wrong impression.
Let me see about doing a better pass on the A15 once I'm back from my current trip.
Take care,
Anand
madmilk - Wednesday, October 31, 2012 - link
More proof that ARM ISA isn't magically more efficient than x86 in perf/watt.My i7-3720QM Mac can complete Kraken in 2100ms, with a load power consumption of 30W and idle power of 12W (display on at mid-brightness, discrete GPU off). Ivy has very good power gating, so I'll just assume the CPU is consuming 20W. This results in 42 Joules to complete one run of Kraken. The A15 on the other hand, with a differential of 4 watts (again assuming perfect gating at idle) takes 38.8 Joules. In server usage, perf/watt is king. If the best ARM can deliver is 10% better perf/watt at the expense of 5x per-core performance, they're not going to make a dent against Xeon. I imagine V8 could be optimized more for ARM, but the gains there are not nearly as big as before.
Some other observations -
I ran 8 instances of Kraken at once to make use of all the cores and HT, while reducing the effect of perf/watt-killing Turbo Boost. Power consumption was about 65W total, or approximately 55W going into the CPU. Each Kraken finished in about 3700ms, so what we have is 55W*3.7s/8 = 25 joules per Kraken. Much better, but obviously an apples-to-oranges comparison against the A15 which should probably have two instances run on it for optimal efficiency.
Also, shame on Intel/Samsung/Google for the Chromebook 500. 12W idling for a netbook is just ridiculous.
I don't think we can pull the 32nm vs 22nm fab card here either, because Intel has always been ahead in this respect and the gap is widening.
lemonadesoda - Wednesday, October 31, 2012 - link
The new chromebook is a near-winner! While it is targetting impulse purchase, low-budget buyers, and 2nd world economies, they should consider a 1st world premium buyer audience. If this had a better quality screen with "retina" pixel density, I would buy one in a heartbeat. I don't want to game... I want to read my PDFs without having to zoom to make the text legible... and with the SD card reader... it would be a perfect image display device for the SD cards once it comes out of the camera. 1366x768 is very 2009, not 2012.ol1bit - Wednesday, October 31, 2012 - link
I don't understand why Chrome OS continues at all?Just slapping JellyBean on this hardware would have much more functionality.
andrewaggb - Wednesday, October 31, 2012 - link
Only google can answer this question....Kinda like Firefox OS... or whatever they are calling it. Just not sure what the point is. Maybe they figured linux needs just a few more radically different distributions :-)
ssddaydream - Wednesday, October 31, 2012 - link
Please, will somebody ban this clown?ShaneMickey, that is...
ssddaydream - Thursday, November 1, 2012 - link
...there will be support that would allow AndroidOS, Linux, or Windows RT to be installed and properly functioning on this device.