NAND Performance

The $199 Nexus 7 ships with 8GB of NAND on-board in the form of a standalone eMMC 4.41 package from Kingston. The single package storage solution features NAND and controller, although as you can guess there's no room for DRAM. The NAND in use is MLC although it's not clear whether we're looking at 2 or 3-bits per cell. This basic architecture shouldn't be all that unfamiliar to long time AnandTech readers - the cacheless design is exactly what plagued some of the early MLC SSDs for PCs a few years ago.

More recently users have been noticing very poor performance with ASUS Android tablets whenever there's substantial background IO going on, particularly multitasking while writes are taking place (e.g. downloading a torrent and browsing the web). The slowdowns range from multi-second long pauses to sluggish response time. The video below shows you what can happen on a Transformer Pad Infinity while downloading a bunch of large files in the background:

Even though downloading a large file is a largely sequential write operation, any other action performed while that download is in progress will effectively turn the IO stream from purely sequential to pseudo-random. Most of these eMMC and other cheap MLC NAND flash controllers are really glorified SD cards, primarily optimized for reading and writing large images as if they were used in a camera. What they're not designed for is to run and be used in a full blown multitasking OS. Some manufacturers seem to do a better job of picking their storage solution, and the Kingston eMMC in the Nexus 7 is faster than the Hynix e-NAND ASUS has used in previous tablets. Neither is perfect however. There's a tangible impact on simple multitasking if you're downloading a lot of files or installing apps in the background. Even operations in memory are quite negatively affected by background IO. Take a look at how SunSpider performance is hurt by a background file download:

SunSpider 9.1 Performance
  Default With 2MB/s Background Download
Google Nexus 7 (8GB) 1665.9 ms 1984.9 ms

To put all of this in perspective, I turned to Androbench, a storage benchmark that allows an ok amount of flexibility in configuring the test environment. At its default settings the benchmark varies a bit too much for my liking, but if you up the buffer sizes to 100MB it helps smooth out some of the variance.

Here we're looking at both sequential and random IO, the two sides we pay attention to in our SSD reviews as well. It's not clear to me whether or not Androbench is clamping the random IO to a particular range of addresses or not, but the results are telling nonetheless:

Androbench (100MB read/write)
  256KB Sequential Read 256KB Sequential Write 4KB Random Read 4KB Random Write
ASUS Transformer Pad Infinity (64GB) 15.9 MB/s 7.13 MB/s 4.90 MB/s 0.22 MB/s
Google Nexus 7 (8GB) 23.1 MB/s 8.43 MB/s 4.77 MB/s 0.32 MB/s
Samsung Galaxy Nexus (16GB) 26.8 MB/s 7.29 MB/s 7.46 MB/s 0.23 MB/s

Sequential read/write speed isn't bad, but it's the random write speed that's really a problem. We're talking about write speeds of a couple hundred KB/s. Remember what I said earlier about how multitasking can take an otherwise sequential IO stream and make it look fairly random? I suspect the low random write performance is one reason we're seeing significant slowdowns with background IO. Not all NAND controllers do well with concurrent reads and writes, which could be another contributing factor to poor performance.

Note that for light usage this isn't a problem. Similar to the first generation of affordable MLC SSDs for PCs, as long as you're doing a lot of reading you'll be ok. It's really for the heavier usage models that this is a problem. On a tablet however, simple background installation or downloading of files counts as heavy these days.

The real solution to this problem is to integrate better NAND flash controllers on-board, or even onto the SoC itself. Tablet makers are still mostly focused on cost cutting, but eventually we'll see real SSDs with good controllers in these things. Windows 8 tablets, at least the high end ones due out later this year will be among the first to incorporate real SSDs.

WiFi Performance, NFC

The Nexus 7 includes support for single spatial stream 802.11b/g/n on 2.4 GHz only. That ends up being a PHY rate of 65 Mbps (single spatial stream with no SGI). ASUS has been using AzureWave modules for basically every single one of its tablets, and the Nexus 7 is no exception. Thanks to the FCC test reports, you can see an AW-NH665 module alongside the new NXP PN65 NFC controller. The AW-NH665 includes a BCM4330 inside - remember there are different vendors who will sell you a completed module.


NXP PN65 NFC, AzureWave AW-NH665 (Source: FCC Internal Photos)

If you're looking for a cost cutting measure, the lack of 5 GHz WLAN support is most definitely one. In fact, the lack of 5 GHz WLAN made for probably one of my most memorably hilarious Google I/O experiences, since the event had multiple signs noting that only devices with 5 GHz WLAN would work well (or at all - 2.4 GHz is unuseable at any major event) on the conference WiFi. To mitigate this, Google hooked up USB OTG to MacBook Air ethernet adapters for its Nexus 7 demo stands, which I of course hijacked for my Galaxy Nexus at one point. More and more, having 5 GHz WLAN in a tablet is an expectation, and soon we'll even start seeing 2x2:2 antenna configurations.

The resulting performance is pretty par for the course when it comes to WiFi speeds among single spatial stream 2.4 GHz only devices. I tested using iperf the same way I do smartphones. 

WiFi Performance - iPerf

Unlike some of the other ASUS tablets of note, there are no reception issues with the Nexus 7 either. I have no problem getting good reception and see the Nexus 7 fall off the network where I expect it to in my area. I think it's worth being explicit about where the antennas are located since wireless connectivity issues have been a recurring issue for just about every product. 


BT/WLAN (red), NFC (blue), GPS (green)

I've gone ahead and marked where the antennas are for BT/WLAN, NFC, and GPS on the case from the FCC teardown photos. Knowing exactly where the NFC coil antenna is located is actually hugely important for correctly positioning the device for beaming or reading tags. It ends up being right behind the "nexus" recessed lettering on the back, but until I saw the antenna in the FCC teardowns I wasn't completely sure. With a smartphone the size makes it relatively forgiving, but tablets are less forgiving about positioning not being exact thanks to the larger size. 

GPS

The Nexus 7 uses a monolithic Broadcom BCM4751 GPS receiver, which we've seen in other devices like the iPad 2. This isn't the absolute newest broadcom GPS/GNSS, and again I'm sure ASUS was able to secure great pricing for this since the newer GNSS (GPS+GLONASS) modules are making their way into devices right now. 

That said, I had no problems with GPS locking quickly from cold and warm starts. I walked around San Francisco with the Nexus 7 using Google Maps (tethered to an SGS3) and saw pretty good performance in the urban canyon scenario. With no occlusions to the sky, performance is excellent, and locks indoors are possible too. 

 

GPU Performance Battery Life
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  • ericore - Friday, July 27, 2012 - link

    Assuming the price is 299 for the entry 16 GB version of Nexus 10, I will only buy it under the following conditions:

    -storage option
    -2GB Ram
    -Preloaded with Ubuntu (duel boot)
    -Option to load other distros in its place

    Linux complements Android very well and fills a lot of the gaps.
    It would be a smart move on Google's part.
    It would be my move.
    Reply
  • richough3 - Friday, July 27, 2012 - link

    I would be tempted to buy this but the lack of decent speakers on a tablet like this is one of the deal killers for me. The other one is the lack of an SD card slot. Sure, it's up to preference, but the way I see it is more and more ISPs are moving to tiered services, so to do everything across the cloud will cost more. Reply
  • Chesher - Friday, July 27, 2012 - link

    Nexus 7 has bluetooth - Kindle Fire does not.

    So, I can use Google Play with my bluetooth speakers with my Nexus 7.

    Just wanted to mention this - because this is a big deal.
    Reply
  • tssynergy - Saturday, July 28, 2012 - link

    Moore's law is in full effect in the tablet world. Given the recent technological progress in components and the slew of new hardware about to hit the streets, I think the differences in the actual devices will become narrow to the point of being insignificant (excluding Windows RT/8, primary computing tablets for now). The key differentiation, in my opinion, lays in the various ecosystems. iTunes vs. Amazon vs. Google Play is where the battle will be won or lost. Sustainable competitive advantage on hardware will be short lived to non existent. Reply
  • ssddaydream - Sunday, July 29, 2012 - link

    While I agree for the larger portion of the market, I think the enthusiast market cannot be ignored. There will always be those who want the absolute best hardware and will just load up AOSP/AOKP. I think the enthusiast market will find a way to bring multi-platform support to their device. Reply
  • Diogenes5 - Sunday, July 29, 2012 - link

    Anyone that thinks Windows 8 Tablets will be competitive at all are fooling themselves. People use Windows devices because they have to, not because they want to. i5/i7-based designs don't offer the kind of battery life and form factor needed for what people have come to expect in the storage space and Tegra 3/ARM based windows 8 tablets offer nothing more hardware wise than current tablets.

    That leaves only the GUI and OS as the differentiating factor between Windows Tablets and Current Tablets. Do people really think that Windows 8 will offer anything near the experience of current android and iOS tablets? Everyone using the RC (including me) is underwhelmed. This is the same Microsoft that produced tablet laptop's for years that nobody bought. Thanks but no thanks, Windows 8 will be a laughingstock just like windows phone.
    Reply
  • maximumGPU - Monday, July 30, 2012 - link

    Another troll..
    all you provide are your opinions and you think they're a reflection of the majority.

    "People use Windows devices because they have to.." plenty of other OS out there if you don't like windows. And guess what? a lot of people do like it.

    "Do people really think that Windows 8 will offer anything near the experience of current android and iOS tablets?" Euh yeah it will, how about proper compatibility and seamless transition between your pc and your tablet for a start?
    I'm a New Ipad owner, and i find the OS very limiting. Awaiting a windows tablet.

    "Everyone using the RC (including me) is underwhelmed.." have you used it in a tablet environment? thought so.

    "Thanks but no thanks, Windows 8 will be a laughingstock just like windows phone". Of course, you'd know that already.
    Reply
  • shaolin95 - Sunday, July 29, 2012 - link

    I was very happy when I saw this tablet first until I read about not SD card options...totally killed it for me...very lame. Reply
  • bertiebond - Monday, July 30, 2012 - link

    but the samsung tab 7.0 (p1000) i use has 3G, has micro SD slot.

    7inch is perfect size for on the go, emergency phone in a pinch, read comics, books, films.

    Nexus, much better hardware specs all round, but critically crippled for what you actually want to use it for.
    Shame really. Samsung sucks with OS upgrades, you have to root it just to get ICS, nevermind jellybean!
    Reply
  • seanleeforever - Tuesday, July 31, 2012 - link

    " In every sense outside of portability, a 10-inch display is much nicer to look at than a 7-inch one in my opinion. There's less zooming in you need to do on web pages or magazines. Text in general is just easier to read and perhaps I'm getting too old, but there's something nice about everything being comfortably bigger.
    Read more at http://www.anandtech.com/show/6073/the-google-nexu...
    "

    really, anand, really?
    would you say the 17 inch notebook is much nicer to look at than 12 inch one?

    my company laptop is a pain in the ass 17 inch dream color elitebook, but i find myself using 12 inch thinpad x unless i absolutely have to do use the company laptop. it is not always the bigger the better.

    with that said, i have both ipad 3 and nexus 7, and my experience has been entirely different from yours. the ipad3 is way to heavy as a tablet, and if i have to use a dedicate carrying device, i find myself using 12 inch laptop most of time. the nexus 7, however, is so light (which you should really focus more in the review IMHO) and allow you to use to use it like a tablet. it also magically fit in all my pants and as someone who travels 70% of time, this is a god send.

    apple is making a big mistake not to release the mini ipad, and now the market is taken.
    Reply

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