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.


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
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  • yun - Tuesday, July 30, 2013 - link

    That's ok, they already know more about me than I do!
  • superflex - Tuesday, July 30, 2013 - link

    Precisely. More government data collection.
    Time to target those evil viewers of Fox News or Duck Dynasty.
    FU Google.
  • StormyParis - Tuesday, July 30, 2013 - link

    You're in luck: get a $50 USB stick (MK808...)
  • Aravot - Friday, August 2, 2013 - link

    I am using Android powered mini-PC MK808, bought it from ebay for $45 including shipping, works perfectly.
  • BryanDobbins - Saturday, August 17, 2013 - link

    like Lillian said I am startled that any body can profit $7923 in 4 weeks on the internet. did you look at this web site...
  • Mikuni - Monday, July 29, 2013 - link

    inb4 $50 or more for Europe.
  • arnd - Monday, July 29, 2013 - link

    Interestingly, the /proc/cpuinfo output shows that the 88de3005 uses a single Cortex-A9 CPU core, rather than Marvell's own PJ4 core that is in the dual-core 88de3100 (Armada 1500).
  • rudolphna - Monday, July 29, 2013 - link

    lololololol I love your wireless network names/computer names. Skynet, l33tn3ss? Molybdenum? Lol awesome man.
  • Brian Klug - Monday, July 29, 2013 - link

    Ha, I'm glad someone liked those :)

  • dvinnen - Monday, July 29, 2013 - link

    I was planning to get one of these for traveling for work but you made it seem like a pain plus having to use a hotspot. It makes sense I guess and I didn't really think out that I wouldn't be networked to it over hotel wifi. I'll probably still get one to play around with though with it being so cheap.

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