A 1.5 V, 200 MHz, 400 MIPS, 188 μA/MHz and 1.2 V, 300 MHz, 600 MIPS, 169μA/MHz Digital Signal Processor Core for 3G Wireless Applications

摘要

A new high-speed and low-power digital signal processor (DSP) core, C55x, was developed for next generation applications such as 3G cellular phone, PDA, digital still camera (DSC), audio, video, embedded modem, DVD, and so on. To support such MIPS-rich applications, a packet size of an instruction fetch increased from 16-bit to 32-bit comparing with the world's most popular C54x DSP core, while maintaining complete software compatibility with the legacy DSP code. An on-chip instruction buffer queue (IBQ) automatically unpacks the packets and issues multiple instructions in parallel for the efficient use of circuit resources. The efficiency of the parallelism has been further improved by additional hardwares such as second 17 x 17-bit MAC, a 16-bit ALU, and three temporary registers that can be used for simple computations. Four 40-bit accumulators make it possible to execute more operation per cycle with dramatically reduced overall power consumption. These new architecture allows two times efficiency of instruction per cycle (IPC) than the previous DSP core on typical applications at the same MHz. The new DSP core was designed for TI's two 130 nm technologies, one with high-VT for low-leakage and middle-performance operation at 1.5 V, and the other with low-VT for high-performance and low-VDD operation at 1.2V, to provide best choices for any applications with a single layout data base. With the low-leakage process, the DSP core operates at over 200 MHz with 188 μA/MHz (at 75% Dual MAC + 25% ADD) active power and less than 1.63 μA standby current. The high-performance process provides it with 300 MHz with 169μA/MHz active power and less than 680 μA standby current. The new core was designed by a semi-custom approach (ASIC + custom library) using 5-level Cu metal system with low-k dielectric material of fluorosilicate glass (FSG), and about one million transistors are contained in the core. The total balance of its power, performance, area, and leakage current (PPAL) is well suitable to most of next generation applications. In this paper, we will discuss features of the new DSP core, including circuit design techniques for high-speed and low-power, and present an example product.