The iPhone 5 Review
by Anand Lal Shimpi, Brian Klug & Vivek Gowri on October 16, 2012 11:33 AM EST- Posted in
- Smartphones
- Apple
- Mobile
- iPhone 5
GNSS: Subtle Improvements
Section by Brian Klug
Like the iPhone 4S and the iPhone 4 CDMA before it, Apple has gone with the GNSS (Global Navigation Satellite System) leveraging both GPS and Russian GLONASS which lives entirely on the Qualcomm baseband. In the case of the iPhone 4S and 4 CDMA, that was onboard MDM6610 and MDM6600 respectively, both of which implemented Qualcomm’s gpsOneGen 8 with GLONASS tier. Going to on-baseband GNSS is really the way of the future, and partially the reason why so many of the WLAN, BT, and FM combos don’t include any GNSS themselves (those partners know it as well). In this scheme GNSS simply uses a dedicated port on the transceiver for downconversion, additional filtering (on RTR8600), and then processing on the baseband. The advantage of doing it all here is that often it eliminates the need for another dedicated antenna for GNSS, and also all of the assist and seed information traditionally needed to speed up getting a GPS fix already exists basically for free on the baseband. We’re talking about both a basic location seed, precision clock data, in addition to ephemeris. In effect with all this already existing on the baseband, every GPS start is like a hot start.
There was a considerable bump in both tracking accuracy and time to an assisted GPS fix from the iPhone 4 which used a monolithic GPS receiver to the 4 CDMA and 4S MDM66x0 solution. I made a video last time showing just how dramatic that difference is even in filtered applications like Maps.app. GLONASS isn’t used all the time, but rather when GPS SNR is either low or the accuracy of the resulting fix is poor, or during initial lock.
With MDM9615 now being the baseband inside iPhone 5, not a whole lot changes when it comes to GNSS. MDM9615 implements gpsOneGen 8A instead of just 8, and I dug around to figure out what all has changed in this version. In version 8A Qualcomm has lowered power consumption and increased LTE coexistence with GPS and GLONASS, but otherwise functionality remains the same. MDM9x25 will bring about gpsOneGen 8B with GLONASS, but there aren’t any details about what changes in that particular bump.
I spent a lot of time playing with the iPhone 5 GNSS to make sure there aren’t any issues, and although iOS doesn’t expose direct NMEA data, things look to be implemented perfectly. Getting good location data is now even more important given Apple’s first party turn by turn maps solution. Thankfully fix times are fast, and getting a good fix even indoors with just a roof between you and clear sky is still totally possible.
Facebook
Twitter
RSS
276 Comments
View All Comments
themossie - Tuesday, October 16, 2012 - link
The manufacturer's charger uses a set of pull-up resistors connected between the various USB lines, to indicate that the phone can pull maximum current. Unfortunately, every manufacturer (and sometimes different phones) use different resistances.See http://electronics.stackexchange.com/questions/144... for a brief writeup.
For what it's worth, I've only had this problem with iDevices and the HP Touchpad. I own circa-2011+ HTC, Motorola and Samsung phones, and they all work fine with every charger. My Droid 2 Global was my primary work phone until a few months ago, and works great with every charger. Not sure why your wife is having problems there.
crankerchick - Tuesday, October 16, 2012 - link
"The non-LTE phones see a sharp drop in battery life. At least at 28nm the slower air interfaces simply have to remain active (and drawing power) for longer, which results in measurably worse battery life. Again, the thing to be careful of here is there's usually a correlation between network speed and how aggressive you use the device. With a workload that scaled with network speed you might see closer numbers between 3G and 4G LTE."Perhaps you all could devise a test for this? Something like, change your LTE and 3G tests, where you decrease the time between page loads for the LTE test, to simulate doing more browsing since the pages load faster? One data point on this, with a reasonably selected change in page load duration, would be very helpful now that we have this very interesting dynamic clearly visible.
That said, as always, I appreciate the reviews presented here. Always thorough with lots of information to chew on beyond specs and "user opinion on user experience."
Just wish the reviews didn't take so long, but they are always worth it in the end.
TofDriver - Tuesday, October 16, 2012 - link
Thanks for this awesome article. Gigantic work, we'll worth the wait.I've learnt so much.
Would still appreciate it as an ebook, even after the web reading!
Seems like you're perfectionists who love to push limits... To me it does resonate with the team who designed the reviewed product.
name99 - Tuesday, October 16, 2012 - link
"Another potential explanation is that the 3-wide front end allowed for better utilization of the existing two ALUs, although it's also unlikely that we see better than perfect scaling simply due to the addition of an extra decoder."Remember the standard numbers. On this type of integer code:
1/6 instructions are branch
1/6 instructions are store
1/3 instructions are load
1/3 instructions are ALU
This means the usual first throttling point i cache access, if you can only do one load/store cycle.
If you limit your cache to one op/cycle, it's generally not worth going beyond 2-wide --- too often you're waiting on the cache.
Once you widen your cache (usually, at this stage, by allowing simultaneous read and write per cycle) three-wide makes sense.
Each cycle now (on ideal and some sort of "average" idealized code) you can now do some sort of combination of half a branch, 1.5 load/stores, and 1 ALU. Meaning that 2 ALUs (as long as they are not overloaded and also handling some aspect of the load/store) is enough for now.
[Of course things never work out quite this ideal --- you have burstiness in operation types, not to mention delays. But the compiler should try to schedule instructions to get this sort of average, and likewise the re-order queues will do what they can to shuffle things to this sort of average. 2ALUs helps with the bursts, 3ALUs is overkill.]
So I would say the primary important change made to go to three-wide in a way that is not a waste of time was to convert the L1 cache to dual-ported, supporting simultaneous load & store per cycle.
jiffylube1024 - Tuesday, October 16, 2012 - link
I have to commend the Anandtech team for the great review! It was a long wait, but well worth it. The info on anodizing, the "Swift" CPU @ 1.3 GHz, camera performance, etc. was worth waiting for. This article, in my eyes, is a culmination of the Anandtech team's knowledge in the tech industry - deconstructing A6 to figure out what it's made of, discussing Apple's manufacturing capabilities, etc. Very informative and well written!I am always amazed at how many complaints (and petty platform wars) get exposed on the comment board. I certainly appreciate them when an article is poorly written, contains false information or outright lies, but with an article like this, the comments section seems shy of the effusive praise it deserves!
------
On a slight tangent, I've enjoyed the first 8 Anandtech podcasts as well, and I have to say that I look forward to more non-iPhone related disucssion on future podcasts. The information was much appreciated, but for a tech site as broad as Anandtech, the first 8 podcasts have been VERY iPhone heavy in their content! Keep up the good work.
jamyryals - Thursday, October 18, 2012 - link
I think you're right, it has been iPhone heavy, but the start of the podcast kind of lined up with the launch/review process. Let's be honest, it is a huge selling high quality device and it's treated as such. I have a feeling Brian and Anand will have a lot to say about all of the impending Nexii/WP8 when they come out this quarter.krumme - Tuesday, October 16, 2012 - link
Good to see reviewers apreciation of low light capabilities for the BSI sensor, reflecting real world usage. Oposite to a lot of uninformed stupid reviews on the net.Its exactly the same practical difference between s2 and s3 cameras. Big difference for real usage.
All the mpix race must stop now. 8M is way to much for the quality anyway.
Zanegray - Tuesday, October 16, 2012 - link
I love the level of analysis and attention to detail. Keep it up!mrdude - Tuesday, October 16, 2012 - link
Wow, what an article. Really fantastic read. The lengths you guys have gone to in this review is stunning, frankly. Well done. Although I'm no Apple fanatic, I must say that this is one of the better articles I've read on AT :)Dennis Travis - Tuesday, October 16, 2012 - link
Totally outstanding review. You guys covered everything. Thanks so much!