Inside Qualcomm's Snapdragon 845 for PCs, mobes: Cortex-A75s, fat caches, vector math, security stuff, and more
Specs, features summarized
But wait, there's more
As well all this semiconductor nerd stuff, the 845 has various things to make next year's smartphones using the silicon take better photos and video and do better at machine-learning tasks – the kind of thing normal people will notice immediately over their older handsets.
One thing Qualcomm was a little sore about is that it has been designing chips for years that can crunch vector math calculations rapidly in hardware, in its GPUs and its DSPs. These vector operations are crucial in machine-learning software, and being able to do them quickly in specialized hardware as opposed to slowly on general-purpose CPUs means things like AI-based image recognition and non-trivial picture processing can happen in realtime. Which makes users happy.
However, unlike a few other vendors, Qualcomm didn't slap an "AI processor" or 'neural network chip" label on its stuff, so now it's grumpy that it looks like it's behind the times, when really, its chips have been accelerating machine-learning inference code for ages.
And related to this, Qualcomm has kept its vector-math units generic, in that, they can handle whatever task you want to assign them, rather than forging dedicated processing units that do one or two particular tasks really well. Qualy's engineers see that as wasted silicon: when you're not running one of those specific workloads, the transistor gates for it are sitting dormant, whereas the fully programmable vector math units in the Snapdragons can crunch whatever is needed next – graphics, AI inference, image enhancements, audio processing, etc.
As such, the 845, like its predecessors, tries to provide a mix of computational engines for developers to enlist as required on the fly. The latest chip's Kryo CPUs are good for 32-bit floating-point and 8-bit integer math (INT8 being very important to AI), the Adreno 630 GPU offers 32 and 16-bit floating point, and the Hexagon 685 DSP block is good for 8-bit integer and HVX – its vector extensions. You can program the bare metal of the DSP if you wish.
The upshot is that, in Qualcomm's mind, the 845 has a decent amount of vector-math grunt for performing AI algorithms on the device, allowing apps to do stuff like inference and detection rapidly without burning through the battery. It supports Caffe, Caffe2 and Tensorflow, and the tech can be accessed via the Neural Processing Engine SDK.
The 845's Spectra 280 image signal processor can capture Ultra HD Premium video: 4K resolution video at 60 frames per second, with 10bit-per-RGB-color and the Rec.2020 color gamut. That's 30 bits of color per pixel as opposed to 24 bits. It can also capture up to 32Mp total from up to two cameras, and record slow-motion 780p video at 480 frames per second.
Graphics-wise, it can playback 4K video at 60 frames per second, as standard, and can drive two 2,400 x 2,400 pixel virtual-reality displays at 120 frames per second, apparently.
The GPU can also be preempted on a primitive boundary: in other words, while rendering polygons to the screen, the running thread can be stopped at the next primitive and be told to render something else. Normally, there's a little bit of runway that a GPU has to land on before it can be switched from its current operation to another. This is supposed to be essential to realtime stuff like VR.
The GPU can also be used to perform foveation, where the most detail in a scene is concentrated at the center of view, where our eyes are most sensitive. That saves you having to render full-quality graphics across the VR display, which is inefficient because the viewer's eyes can't pick out that level of detail.
Instead, you show the most detail in the center of view and drop to a coarse-level outside that area. The Adreno unit will help identify where the viewer is looking and optimize the display for that center spot, which again is good for VR.
Another neat trick supported by the chipset is something called ImMotion, a post-processing technique where the user marks out an area of a video where motion is happening – such as a goldfish swimming around a bowl – and the system produces a cinemagraph of the scene.
The resulting video has the goldfish swimming in a looping animation while the background, a child staring at the bowl, for example, remains motionless, creating a poignant moment. Here's some example cinemagraphs to get the idea. It could be neat.
The 845 also comes with Qualcomm's X20 LTE mobile broadband modem, which can download stuff at up to 1.2Gbps, obviously depending on your network, plan, and reception. The chipset also supports multi-gigabit 802.11ad Wi-Fi, 2x2 802.11ac MU-MIMO Wi-Fi, and dual SIM-dual VoLTE – which means both SIMs in the handset can each get full access to voice-over-LTE at the same time.
One final thought: around spring next year, Snapdragon 835 Windows 10 PCs are coming. If they don't sound powerful enough for you, well, it sounds as though Snapdragon 845 PCs are coming closely after. You may want to hold off to this time next year to get your hands on an 845-powered laptop-tablet.
A product brief of the Snapdragon 845 can be found here [PDF]. ®