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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  • someone0 - Monday, August 22, 2011 - link

    The author start confusing when he trying to prove that there is no hardware problem by saying that the CPU is fine. I'm sure a lot of people here have built their PC before. So, the analogy that CPU=hardware is not valid. Even given that it's CPU package, still shouldn't the author treat the tablet PCB like a motherboard. The whole article totally ignore the existance of the PCB. I'm sure the argument that the software/OS is not optimize, but it is iffy to start blanking a variable here and dumping the whole problem on OS. I guess this answer will be fully answer when we start seeing Android custom ROM on the tablet. But either way the fault still on HP regardless of whether it's hardware or software. Reply
  • tipoo - Saturday, December 10, 2011 - link

    SoC, not CPU. There's a reason these are called System on a Chip(s). Reply
  • bobbozzo - Monday, August 22, 2011 - link

    1. s/morover/moreover/ on Page1

    2. the CPU instruction set revision should be largely irrelevant:
    it's Linux, so it's C, not assembly; therefore it's mostly just a matter of re-compiling. Yes, SMD optimizations (if done manually) are an exception.
    Reply
  • p05esto - Tuesday, August 23, 2011 - link

    I picked up two 16GB Touchpads for my wife and I at Best Buy Saturday night. ...and I'm KICKING myself for not getting the 32GB versions they also had there. A few movies later and my device is already full. I wish it had a FlashCard reader for additional memory, that part sucks.

    But other than that I really LOVE this tablet. The email program is better than Outlook and the other webmail systems I use. The browser renders nice and some of the games are great. The $10 Need for Speed game is AMAZING, the graphics are fantastic, no lag, great detail. I can't believe how good the graphics are on this thing. It totally blows the iPad away in the gaming/graphics power area. It's got a dual-core 1.5ghz CPU which you can overclock to 1.7 with a little effort.

    In short, for $100 this was the deal of a lifetime for me. I had no interest in tablets before (due to price point), but now I'm in love. It sure beats a laptop in bed/couch for casual email and web browsing. Also great for movies on the go for the kids or games to keep them all busy.

    I hope HP opens up WebOS to the devewloper community, this little platform could really flourish if opened up to all for free. Open source could make this thing take off. With a few tweaks in the UI and cusomtization department I can see the TouchPad becoming a legenday device, a coveted item to own and something that another manufacturer will want to start developing hardware for!
    Reply
  • Chadder007 - Tuesday, August 23, 2011 - link

    And what....HP wants to be just a Software company now? LOL Reply
  • Zextegra - Tuesday, August 23, 2011 - link

    Sorry I do not agree with your article. People buy to much into these benchmarks used on tablets and phones. They are inaccurate and unproven. Also the architecture of the CPUs look good on paper but most do not understand them and only take what the engineers have to say. I believe the snap dragon is the AMD in this tablet war and the a5 is the intel. I think once we see another os ported on the touchpad that soc was a large part of the fault. Reply
  • spunkybart - Wednesday, August 24, 2011 - link

    I'm mostly an Apple guy (iPad, iPhone, iMac, iPod...), but I was rooting for WebOS -- I had heard it was a decent OS. Apple needs competition so that Apple products get better (and to give users an escape hatch if Apple keeps trying to control user content too much!)

    What surprised me most was how fast this all went down. If HP wasn't fully committed to WebOS and tablets for the long haul, then why'd they spend money and time on buying Palm and developing a tablet? It just seems a colossal waste -- and surely a morale buster inside the company.
    Reply
  • amorexue - Sunday, September 25, 2011 - link

    this is my site www.loveweddingdress.co.uk Reply
  • mattj7 - Wednesday, March 28, 2012 - link

    I recently put Cyanogenmod 9 alpha 3 on my hp touchpad, and the difference is night and day. I honestly thought this was an under powered tablet because of the performance I was getting on webos. NOPE, with android this baby flies! I'm sure the asus transformer prime or ipad 3 would put it to shame, but it has all the power I need to game, browse pdfs, web pages, video, whatever, and Cyanogenmod 9 is still in alpha and full of bugs! But it has the hardware acceleration and thats probably the biggest jump in performance.

    It's not the hardware, it's webOS holding back the touchpad. As much as I liked the swipe gestures, the deserted app market, and laggy performance makes having android on it all the sweeter!
    Reply

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