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
POST A COMMENT

118 Comments

View All Comments

  • The0ne - Friday, July 27, 2012 - link

    My Kindle is fulled with books and audio books and I need more space. I am seriously thinking about purchasing the Nexus 7 as a replacement simply because XDA has provided a way to add more storage space via a dongle. Still, my eyes are shouting for a 10" reader as I know the 7" Kindle is always stressing as it is. Reply
  • robinthakur - Tuesday, July 31, 2012 - link

    I would imagine it is the beginnings of an anti piracy drive as that is such a hot topic on Android and a key reason why some app just aren't available for it. Which is a great shame as having a Micro SD slot is emminently useful and cheaper than paying for manufacturer added storage. Reply
  • TheJian - Wednesday, August 01, 2012 - link

    iphone collection packs are readily available on newsgroups and websites. No more piracy on android than ios. That's a fallacy perpetuated by apple lovers. Nothing sneaky about leaving off a micro sd slot. Dead trigger was given away because of one of two things: The game sucks an reviews show it, or they just are apple lovers who ported it to give it away to hurt android. Why would you give your game away due to any piracy? No amount would make a sane person give away their work for good. There are NO honest people on android?...LOL. Sounds like a scam to me. How does angry birds make money then? OK, a 3rd option; they saw sales sucked so went with whichever had better sales and publicity stunt for the other platform (in this case android). I'd venture to guess sales still suck on IOS too... :) No amount of publicity crap will fix reviews in the 40's. Rovio isn't complaining about android sales.

    Does your ipad3 come with micro sd? Must be because of all that piracy huh? Sounds like BS both ways eh? For $200-250 what did you expect to get? They blew away the kindle fire, asking much more is asking for the impossible at this price.

    Make a better game that people enjoy (and isn't just a gpu fest) and it will sell. End users don't crack games, professional groups do and they do it just as well on ANY platform (including the PS3 now). Heck you can buy an xbox360 pre modded and ready to happily play your copies. Yet, for some reason people spew comments about PC's being so easy to pirate on...LOL. PC games have craploads of patches, thus needing more skilled users to update and crack said updates. I'd say it's tougher on a pc, where any monkey can buy a pre-modded console and boot a burned game from release groups.

    As someone already said, most users can't even copy/delete files. Witness the number of people in forums etc asking why their pirated PC game doesn't work. "the game says insert disc etc, where's the crack?"...Umm, gee, did you check the \crack folder? Bother to read the nfo file?...ROFL. Followed by the inevitable "how do you open a .nfo file?" and it goes on an on. Worse, some just can't get past "how do you open a rar file, or .001, or .part1.rar"...At some point someone says RTFM or "google it" :)
    Reply
  • robinthakur - Friday, August 31, 2012 - link

    The fact of the matter is that there is little incentive to jailbreak an iDevice anymore because Apple has added most of what was missing previously. You also lose alot like when Apple release a new iOS and you have to wait for it to be jailbroken.

    However, for most Android users who do not own first party Google devices (at least the ones that still get updates...!). you need to root your phone to install updates in a timely manner. On most FAQS about rooting your phone there is inevitably a section discussing pirated apps. The availability and proliferation of pirate apps for Google is certainly nothing new, perhaps you have been willfully ignoring it. The stats on it from most of the developers who mention it are absolutely shocking.

    This is the downside of having more technically adept users I suppose, but to pretend that it either doesn't exist or even more crazily that iOS developers release thei product on Android free to hurt the platform (hmm...) is paranoid delusional.

    The fact is that Angry Birds on Android is free and *ad-supported*. It is not free. Rovio is at least canny enough to realise that the target market aren't prepared to even pay 1.99 for their hard work, and even those playing ad-supported games still complain about the in-game ads and use ad-blocking software so that still doesn't solve the problem. The 360 and also PS3 do ban users that they detect using pirated software online (everyone seems to play multiplayer these days) so no it is not just as easy to pirate on console to how easy it is on the PC.
    Reply
  • GTForce - Thursday, July 26, 2012 - link

    I think it should be "winning a higher level accolade" instead of "winning a higher level allocade". It's always baffling to see pro tech editors not using a simple spell-check to finalize their articles. BTW, a nice article (as usual on AnandTech). Reply
  • CeriseCogburn - Sunday, July 29, 2012 - link

    Pro or Moe ?
    Arrogant and ignorant.
    Imagine the heady region in where they dwell.
    If they need a spellchecker, they must be stupid.
    It's fear and low self esteem.
    Reply
  • tipoo - Thursday, July 26, 2012 - link

    I'm curious now if a better flash memory controller is part of what gave iPads the fluidity lead up until this tablet, how do they fare in NAND performance? Reply
  • wendoman - Thursday, July 26, 2012 - link

    "The video below shows you what can happen on a Transformer Pad Infinity while downloading a bunch of large files in the background:"

    Where the video?
    Reply
  • driscoll42 - Thursday, July 26, 2012 - link

    You don't actually lose Amazon's video service. You can view Amazon Prime videos in any standard browser, I've got a shortcut on my Nexus 7 which just goes straight to Amazon's Video Service. What you do lose is access to the Lending Library. Reply
  • geniekid - Thursday, July 26, 2012 - link

    Good point. I use Amazon VoD a lot, which is the best argument for myself in getting a Kindle Fire over this thing.

    I wonder what the difference between the KF and Nexus 7 is in terms of how long it takes to get from the home screen to actual streaming video.
    Reply

Log in

Don't have an account? Sign up now