It's Really Not Qualcomm's Fault

We've established that webOS has been and could be ported to different SoCs from different vendors – there's nothing tying it irrevocably to Qualcomm. The next is a discussion of the performance delta that existed because of differing hardware between tablet vendors. The Next Web wrote a story today claiming that webOS could run over 2x as fast on an iPad 2 than on an HP TouchPad. The claim gets even more interesting:

"With a focus on web technologies, webOS could be deployed in the iPad’s Mobile Safari browser as a web-app; this produced similar results, with it running many times faster in the browser than it did on the TouchPad."

I'm going to ignore the whole "because it's webOS it can run in a web browser" argument but let's get to the performance discussion. While webOS and Mojo do make substantial use of JavaScript, CSS, and HTML5, that doesn't necessarily mean the entire OS itself can be a web application. Don't forget the Palm PDK as well, which runs much closer to metal than the Mojo SDK.

Anyhow, the TouchPad uses Qualcomm's Snapdragon S3 APQ8060. It has two Scorpion cores running at 1.2GHz, a shared 512KB L2 cache and a dual-channel memory controller. In the TouchPad there's only a single 1GB DRAM on board. It's unclear if there are two DRAM die on that package or not, so whether or not the SoC is actually given full access to 2 x 32-bit LPDDR2 devices is unclear. The CPU cores are in-order and feature a pipelined FPU and NEON unit. On the GPU side the APQ8060 uses Qualcomm's Adreno 220.

If this hardware sounds familiar to you it's because it's the modem-less version of the MSM8x60, the same SoC used in the HTC Sensation and the EVO 3D.

The iPad 2 uses Apple's A5 SoC manufactured by Samsung. It has two ARM Cortex A9 cores, a 1MB shared L2 cache and a dual-channel memory controller. The A5 in the iPad 2 comes in a PoP (Package-on-Package) configuration with the DRAM stacked on the SoC die. Although it's physically unclear whether both channels are populated, the Samsung DRAM part number on the A5 indicates a PoP stack with two DRAM devices. In other words, the A5 is running in dual-channel mode. The CPU cores are out-of-order, feature a pipelined FPU and NEON unit. Imagination Technologies supplies the PowerVR SGX 543MP2 GPU in the A5.

From a CPU standpoint, Apple has a performance advantage at the same clock speed, but Qualcomm runs its cores at a higher clock. NVIDIA claimed that the move to an out-of-order architecture in the A9 was good for a 20% increase in IPC. Qualcomm has a 20% clock speed advantage. In most situations I think it's safe to say that the A5 and the APQ8060 have equally performing CPUs.

Apple does potentially have a memory bandwidth advantage as it's unclear the memory configuration of the TouchPad. I did wonder if this might be a reason why UI transitions were so slow on the TouchPad. In order to deliver a smooth UI you need good GPU acceleration built into your OS and you need sufficient memory bandwidth for the screen. At 1024 x 768 you need 180MB/s of memory bandwidth to render a UI at 60 fps. That's assuming no overdraw or multi-pass blending effects. With only a single LPDDR2-667 channel there's only 2.7GB/s of theoretical memory bandwidth. In practice you generally get 80% of peak theoretical memory bandwidth, that takes us down to 2.1GB/s. If we assume webOS was really inefficient in drawing its UI and needed 7x the bandwidth per frame, that still leaves us with 840MB/s of bandwidth available for the rest of the SoC. Assuming the CPU cores aren't doing anything, that's enough to provide a smooth, 60 fps UI. Start taxing those CPU cores and their bandwidth demands could go up to a few hundred MB/s, perhaps even more. Let's not even mention what happens if the GPU starts cranking away.

Now if we assume that webOS is super efficient, then even a single LPDDR2 channel is more than enough to deliver a high speed UI. In my calculations above I assumed a 7x increase in memory bandwidth requirements per frame. If we knock that down to 4x we nearly double the amount of memory bandwidth available to the rest of the SoC.

My point here is that the Qualcomm hardware is technically fast enough to deliver a smooth UI in webOS. The problem wasn't the hardware.

As far as CPU performance goes, here's a graph comparing the Tegra 2 based Galaxy Tab 10.1 to the A5 based iPad 2 in Sunspider 0.9:

SunSpider Javascript Benchmark 0.9

Granted this test measures the entire hardware and software stack (browser, OS) and does show a ~2x performance delta between the TouchPad and iPad 2, but it shows that it's physically possible to build a tablet that has performance similar to the iPad 2. Furthermore, we've already shown that NVIDIA's Tegra 2 performs similarly to Qualcomm's dual-core SoC in other situations. Completing the circle it's safe to assume that at least from a CPU standpoint, Qualcomm's APQ8060 wasn't the factor holding back the TouchPad, it was software.

The only area where the iPad 2 could conceivably be 2x the speed of the TouchPad due to SoC hardware alone is in GPU performance. However the claims above say the performance advantage was demonstrated in a browser window and not in a cross-platform OpenGL ES 2.0 game.

These days Qualcomm's high end dual-core SoC is comparable to TI's and NVIDIA's. Each platform has its advantages but I find it very difficult to believe that Qualcomm was somehow responsible for the poor performance of the TouchPad. 

It's Not Qualcomm's Fault webOS Needed Work
POST A COMMENT

79 Comments

View All Comments

  • casteve - Monday, August 22, 2011 - link

    Anand:

    A ZDNet article on 8/21 by James Kendrick claims "..There is so much event logging in the background that it seriously impacts the TouchPad’s performance, as it is constantly doing things it doesn’t need to do." He then goes on to show how to disable the logging mechanism. Here's the link:
    http://tinyurl.com/4xwkuat

    How about a quantitative analysis to compare before / after performance? :D
    Reply
  • pwcee - Thursday, August 25, 2011 - link

    I agree, would love to see this done then tested and compared. Reply
  • tipoo - Saturday, December 10, 2011 - link

    Thirded but probably too late for them to test it. Lots of people have said disabling logging makes it pretty zippy. Reply
  • ABR - Monday, August 22, 2011 - link

    Amusingly in the context of the reports of these being sold in stores for $100, the true market value right now seems to be $280. This whole thing is a very dumb move by HP. They had a reasonable thesis when they acquired Palm -- vertical integration within the enterprise. As with Apple, they could and should have started by targetting consumer market first. Now they'll sell it off and give up one of the few legs up they could have had on IBM. Advantage Google/Motorola. Reply
  • GotThumbs - Monday, August 22, 2011 - link

    I've been wondering if anyone has already tried this. Reply
  • tipoo - Saturday, December 10, 2011 - link

    Android is being worked on and there is an alpha out for the Touchpad. iOS is not and will never be open source, so we have no way to port it. Reply
  • Omid.M - Monday, August 22, 2011 - link

    Anand & Brian,

    Would be nice if you could get some devs to speak about working with WebOS and what they think the platform would need to take off, just as an "outsiders' " perspective. You know?

    -Omid

    @moids
    Reply
  • sooper_anandtech12 - Monday, August 22, 2011 - link

    I still fail to see how this is HP's fault. Maybe it's HP's fault in name because they acquired Palm and all its webOS engineers. However, I still feel the issue and problem was an inherent issue of Palm's that HP took on when they acquired them. As mentioned in the article, there are simple ways to have improved the performance of webOS and yet for the past how many years has that not been done precisely? I don't expect a company like HP that's not a software company to be able to step in and say, "Yep, yep. See there Mr. webOS software engineer. Here's your problem."

    If there's anyone to blame, blame Palm and all of the legacy engineers that HP inherited. How much more resources did HP need to commit to webOS when one author of an article on AnandTech can discern a few that would bring notable performance improvements? Scaling the project out by taking more time was not an option, especially when HP is being crucified by the media for taking their sweet time bring a webOS tablet to the market. Then, when they do, they get lambasted because it's undercooked.

    This was a losing proposition for HP no matter how they swung it. Saying that "consumers" were disappointed is giving consumers too much credit. No one mourns the death of webOS. If we did, we'd have been picking up webOS devices from the start, fueling its development. HP was smart by getting out while it still could. Especially in this crazy patent litigating industry, they might even be able to off-load those patents at a profit to el Googs.
    Reply
  • The0ne - Monday, August 22, 2011 - link

    Anand, I appreciate you taking the time to explain some of these rumors and talks but as I read through your explanations I'm asking myself why in the world would you need to. You're basically telling people that because it is a different OS it will require different drives, encoders, decoders and what not. Having to explain this to your audience here is quite pathetic imo. Sure they may be some that are too worked up to see the reasons you've outlined but still, it should have been expected from a more knowledgeable crowd.

    It feels as though you are schooling many of the users here and that is just quite sad. I thought many here were professional enough to have thought this through, pass the drivers and basic necessity that an OS requires. Don't get me wrong, I'm not bashing you, I'm just saying I'm disappointed in the audience because you had to take the time to clear some of these basic issues up. Quite sad.
    Reply
  • The0ne - Monday, August 22, 2011 - link

    Edit:

    Ok, I just read Anand's own Jason Mick's article on WebOS. Yea, great headliner to have people start arguing alright. Do us a favor and fire his stupid a** reporting. If you need brain dead reporters that just pick things without thinking first, go to a pet shop and find a bird or rabbit.

    So with that adding to the confusion and rumors, you're here defending that idiots' reporting. And yes, that was one God aweful thread as well ending with his "I really don't know and I think it's this and that..." comments. Jesus Christ.
    Reply

Log in

Don't have an account? Sign up now