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
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  • LoneWolf15 - Saturday, August 20, 2011 - link

    "There is a clear pattern of bias among his reviews where Quadcomm was always favored, and other chipmakers were marginalized even criticized."*

    * - Citation needed.
  • MrSewerPickle - Saturday, August 20, 2011 - link

    Agreed. If you are an unknown source calling into question the validity of a highly known and respected source then you need facts. Otherwise save it for Facebook or Twitter or where ever else you post non fact based comments.
  • jmcb - Sunday, August 21, 2011 - link

    I have yet to see what you're talking about. And I've been reading on this site for a few years....before I even knew what chips went inside of phones...or even knowing cpus, gpu's were even being used at all in phones.
  • Griswold - Tuesday, August 23, 2011 - link

    Cant spell Qualcomm right but accuses him of being paid by Qualcomm.
  • softdrinkviking - Saturday, August 27, 2011 - link

    pro11y just a troll. I mean, he really pulled that out of his a$$. Just wants attention.
  • jjj - Friday, August 19, 2011 - link

    HP is about to start selling the Touchpad for 100/150$ (16/32 gigs model).
    Bestbuy Canada already is
  • Brian Klug - Friday, August 19, 2011 - link

    I've got Amazon set on check4change in Firefox for when the updated pricing goes live there (supposed to be 8/20). I wonder whether they will also drop the Veer in pricing.

    I was excited for the Pre 3 too, too bad it'll never see the light of day in the USA. Maybe they'll liquidate those stocks too, they must exist somewhere.

  • lorribot - Friday, August 19, 2011 - link

    What worries me is that HP want to turn themselves in to a software company rather than hardware yet it is the lack of software development that has let them down with the whole Palm WebOS piece.

    Hardware is probably the thing that HP has generally done well, granted there isn't the money there any more, but really HP and software what have they ever done in that field?
    VMS, HP-UX remember them? Most of their stuff is crippled by poor development (WebJet admin still won't install on Windows 7) and lack of polish with clunky and flake UIs (WebOS anyone?)
  • z0mb13n3d - Friday, August 19, 2011 - link

    While the article is quite thorough and does give a reasonable explanation of the unfortunate state of webOS, I am more than a bit surprised as to why Anandtech thought it needed to 'clear the air' here. This isn't the first time (and will certainly not be the last) where folks in blogs or forums throughout the internet blame a random vendor for something, but for Anandtech to come out 'defending' a company (Qualcomm in this case) is a bit alarming.

    I've been reading tech blogs and sites ever since they started more than a decade ago and have always been a regular AT reader because of the unbiased nature of your articles and also because AT never really sides with any brand, vendor or company. I sincerely hope this article does not signal a change in the way AT handles reviews and articles in future!
  • sprockkets - Friday, August 19, 2011 - link

    Why it is a bit "alarming"? Either qualcomm or hp would come out looking bad, so either way would it look bad to you?

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