While we were expecting Qualcomm to launch the new Snapdragon 835 as the successor to the Snapdragon 820 in February, Qualcomm surprised us all by launching a capable Snapdragon 821 processor which went on to power a number of flagships like Google's Pixel and Pixel XL and OnePlus' 3T in the last quarter of 2016.
The Snapdragon 821 processor features thrice as fast peak upload speeds and 33% faster peak download speeds compared to the Snapdragon 810 thanks to a X12 LTE modem that offers download speeds of up to 600 Mbps. At the same time, it also brings in 10% increase in performance over the Snapdragon 820 and the new Qualcomm® Hexagon™ 680 DSP facilitates improved performance and power efficiency. An exhaustive AnTuTu examination of Pixel or Pixel XL phones will reveal the real-life performance scores of the new processor. The DSP, says Qualcomm, is "capable of generating photorealistic graphics for console-quality gaming and next-generation virtual reality apps."
Qualcomm's Snapdragon 821 is, however, quite similar to the Snapdragon 820 in many respects. Like the latter, it runs the same Qualcomm® Kryo™ CPU and an Adreno™ 530 GPU but the latter has now been fine-tuned to offer 5% better graphics performance over the former. It also features 14-bit Qualcomm Spectra™ Image Signal Processor (ISP) which offers zero shutter lag in smartphone cameras and lets smartphones run cameras with up to 28-MP in resolution.
Aside from the above-mentioned features, the new Snapdragon 821 can also support up to 4K Ultra HD video capture @ 30FPS, a 4K Ultra HD display, up to 4W output power from amplifiers, HD Voice over 3G and VoLTE and Wi-Fi calling with LTE call continuity. While it isn't really a comprehensive upgrade to the Snapdragon 820, it is still powerful enough to support a number of premium phones until Qualcomm launches the Snapdragon 835 to power next-generation smartphones. Here's a detailed comparison between Snapdragon 820 and Snapdragon 821 for your understanding: