As I reported by the EDA360 Insider more than two months ago—see “Qualcomm renames existing ARM-based Snapdragon mobile application processors and provides future roadmap”—Qualcomm has been discussing the 28nm version of its Snapdragon mobile SoC, called the Snapdragon 4. Now the company has published a 9-page White Paper with many more details about the Snapdragon 4 chip. There are many interesting details, to say the least. Here’s a block diagram of the chip from the Qualcomm White Paper:
The center of the block diagram shows two Krait CPU cores, which are Qualcomm-proprietary implementations of the 32-bit ARM RISC processor architecture. (Note: Kraits are venomous snakes found in Asia and the Krait processor’s immediate predecessor was called the Scorpion. Is there a message there?) At 28nm, the Krait processor cores will run at 1.5 to 2.5GHz but they’re designed for power efficiency in that they have separate, dedicated operating voltage and clock frequency control, allowing the operating software to scale operation of the two cores according to the workload. Either processor can be fully powered off when not needed. The Qualcomm White Paper claims that this approach makes the “big core, little core” approach unnecessary because either of the Snapdragon 4 Krait processor cores can act as a big core or a little core. (See “Processor Wars: NVIDIA reveals a phantom fifth ARM Cortex-A9 processor core in Kal-El mobile processor IC. Guess why it’s there?” for additional analysis of the “big core, little core” approach.) Qualcomm’s White Paper claims that this aSMP (asynchronous Symmetric Multi-Processor) approach delivers a 25 to 40% improvement in operating power for a given performance, as you can see in the following graph:
The Snapdragon 4 SoC also contains a 3G/4G multimode world modem for cellular telecommunications. It can operate using the following telecom standards:
- LTE FDD/TDD (Cat3)
- 3G (DC-HSPA+ Cat 24)
- EDVO Rev B
- 1x Advanced
- TD-SCDMA
- GSM/GPRS/EDGE
In addition, the Snapdragon 4 SoC contains an enhanced GPS modem that operates simultaneously with the US GPS system and the Russian GLONASS system and there is also a collection of on-chip modemsl for local wireless protocols including Bluetooth, WiFi, FM, and NFC (near-field communications).
The Snapdragon 4 SoC also contains three of Qualcomm’s proprietary Hexagon DSPs, a multimedia processor, and assorted audio and video hardware accelerators. But the most important accelerator is likely to be the integrated Adreno 225 GPU (graphics processing unit), which is also a proprietary Qualcomm design. The Adreno 225 GPU is said to deliver 50% more processing power than its immediate predecessor, the Adreno 220 GPU, and 6x the processing power of the initial Adreno 200 GPU.
The Qualcomm Snapdragon 4 SoC is a good leading indicator of the kind of immense integration made possible by 28nm IC process technology.
For more details, download the Qualcomm Snapdragon 4 SoC White Paper here.
EDA360 Insider 