Inside Chromecast

Inside the Chromecast it’s also a simple affair, I took a look at the FCC disclosure for the Chromecast which had internal images up right after the event, and noted inclusion of a Marvell 88DE3005 SoC and AzureWave NH–387 WiFi combo chip. On the backside is 512 MB of Micron DDR3L memory and 2 GB of flash. The antenna for the WiFi combo is printed on the PCB off to the side, there’s no diversity or anything special, just a single PCB antenna.

The Chromecast supports just 802.11b/g/n (2.4 GHz), sadly no 5 GHz is included. That’s somewhat alarming if you’re in an area where 2.4 GHz is congested to the point of being unusable (just about any major urban area), and even more so since streaming applications demand a good QoS for good experience. I have no doubt that 2.4 GHz-only was chosen for cost reasons here, but I would’ve gladly paid $5–10 more for 5 GHz and eliminating that as a potential problem.

Best I can tell, the Marvell 88DE3005 is a cut down, perhaps binned version of the 88DE3100 SoC that has shipped in Google TV for some time now with just a single CPU core enabled. Some hacking done by enthusiasts has confirmed from /proc/cpuinfo that only a single core is visible to the OS, and that the Chromecast also interestingly enough really runs Android, not Chrome, and includes a build.prop file like you’d expect an Android device to.

Google no doubt chose this Marvell SoC in part thanks to the presence of hardware VP8 decode, and I have no doubt YouTube on the device brings down VP8 versions of videos when available, and the Chrome tab to Chromecast streaming uses VP8 as well. Of course there’s hardware decode of H.264 High Profile onboard as well for Netflix and other YouTube videos without VP8 versions. Google lists the supported codecs on their Google Cast SDK page.


Idle


Under Load

Back when the power situation was unknown and still steeped in conflicting information about HDMI power delivery (again, it can't be powered by MHL-HDMI ports which can supply up to 500 mA at present spec, and HDMI doesn't supply enough current, just 50mA), I set about measuring power. I have a handy USB power meter which sits in line with devices and shows a small graph as well as data on its OLED display. I stuck the meter in line between the microUSB power supply provided with Chromecast, and the Chromecast, and measured around 420 mA at peak while decoding either a 1080p Netflix stream or Chrome tab streamed to it, and around 250 mA at idle. All of those are at 5 V, so at peak the Chromecast draws around 2 watts, at idle around 1 watt. Of course if the Chromecast is plugged into your TV’s USB port, chances are when the TV is off power is cut to USB, so idle really is completely off. It’s obvious to me that Chromecast definitely leverages that hardware decoder for both VP8 and H.264 processing to get these very low power numbers.

Introduction and Hardware The First Mode - Cast SDK
POST A COMMENT

105 Comments

View All Comments

  • jjj - Tuesday, July 30, 2013 - link

    This is exciting because it's open and easy for devs to add the functionality while users don't have to wait on Google or install apps on the device to gain functionality. Many more things to say about it but won't do that now, except that i hope they won't censor content and it's a pity they released it when it still looks at best like a beta.Things like local media playback not just tabs, phone to phone , more apps supporting it (including some other Google services like Docs) would have been nice to have at launch.
    Google managed to keep it simple and it's cheap but it's in beta and it's not easy to explain what the thing is to the consumer and they haven't found a great way to do so. Nice to see that Google pulled a Google in a time when they seem to have lost it and it has a strong chance of taking off fast. Now if they would also get rid of that huge "NSA Inside" label on the box....
    Reply
  • darwinosx - Tuesday, July 30, 2013 - link

    It's Google TV code not android. Yet another thing not mentioned in this review. Reply
  • savagemike - Tuesday, July 30, 2013 - link

    It's hard to get rid of a label born of pure accusation. Leaving aside that they have disclaimed the accusation the problem at hand is this. Whatever Google has or has not done - what you are asking them to do now is to get people like yourself to stop saying they have done it. And they have no way to do that. Reply
  • bleached - Tuesday, August 20, 2013 - link

    Third party apps are already playing content through drop box, Google Drive, etc. Reply
  • CommandoCATS - Tuesday, July 30, 2013 - link

    Heh, funny you should note that the Chromecast might be the first Motorola/Google product, since ironically it doesn't work correctly with any of the Motorola OMAP4/Jellybean 4.1 devices (Bionic/RAZR/MAXX/Droid 4).

    https://forums.motorola.com/posts/8a641ae938
    Reply
  • Brian Klug - Tuesday, July 30, 2013 - link

    Weird, even after getting the Play Store updates?

    -Brian
    Reply
  • CommandoCATS - Tuesday, July 30, 2013 - link

    Yup, it seems to be something with the WIFI implementation on those phones. It will sometimes find the device, but be unable to complete the setup (fails after entering AP information). I was able to complete setup just fine with a laptop, and then it will mostly work, but the Chromecast app still doesn't think it's set up. Apparently some features will still be missing, but I haven't explored it fully yet. Reply
  • CommandoCATS - Tuesday, July 30, 2013 - link

    Also, apparently Play Music will not work (from the Motorola device) when it is configured in this manner (from another device). Reply
  • Brian Klug - Tuesday, July 30, 2013 - link

    Wow, that's weird, I'll have to see if I can find my Droid 4 or something, that's bad news.

    -Brian
    Reply
  • darwinosx - Tuesday, July 30, 2013 - link

    A video streaming device that doesn't do 5 ghz? That makes no sense.
    Roku does much more and the Chromecast isn't all that small when you add the HDMI cable and power supply. Which Google went out of their way to pretend didn't exist.
    This review was really too uncritical of the shortcomings of this device.
    Reply

Log in

Don't have an account? Sign up now