A programmable vertex shader with fixed-point SIMD datapath for low power wireless applications

Abstract

The real time 3D graphics becomes one of the attractive applications for 3G wireless terminals although their battery lifetime and memory bandwidth limit the system resources for graphics processing. Instead of using the dedicated hardware engine with complex functions, we propose an efficient hardware architecture of low power vertex shader with programmability. Our architecture includes the following three features: I) a fixed-point SIMD datapath to exploit parallelism in vertex processing while keeping the power consumption low, II) a multithreaded coprocessor interface to decrease unwanted stalls between the main processor and the vertex shader, reducing power consumption by instruction-level power management, III) a programmable vertex engine to increases the datapath throughput by concurrent operations with main processor. Simulation results show that full 3D geometry pipeline can be performed at 7.2M vertices/sec with 115mW power consumption for polygons using the OpenGL lighting model. The improvement is about 10 times greater than that of the latest graphics core with floating-point datapath for wireless applications in terms of processing speed normalized by power consumption, Kvertices/sec per milliwatt.

A 231-MHz, 2.18-mW 32-bit Logarithmic Arithmetic Unit for Fixed-Point 3-D Graphics System

“…11. Radix-4 reciprocal-square-root (RDX4) is also implemented for the performance comparison [2]. The gate counts of LAU and RDX4 are 9 k and 44 k, respectively.…”

A 231MHz, 2.18mW 32-bit Logarithmic Arithmetic Unit for Fixed-Point 3D Graphics System

“…Usually, there are two reasons why the fixed-point number system is used instead of a floating-point number system [2]. First, the hardware architecture of the fixed-point arithmetic is much simpler than that of the floating-point arithmetic because the fixed-point arithmetic uses only integer datapath.…”

“…As 3-D graphics are becoming more and more familiar to people, there have been increasing demands for high-quality graphics for new applications such as avatar, advertisement, and games. Many 3-D graphics processors have been studied [1], [2] to meet these requests. The mobile system has low resolution and a smaller screen size than a PC system.…”

“…However, the mobile system also has limited resources in terms of CPU performance, memory capacity, and battery energy. Most mobile systems use low-power 32-bit processors such as ARM or MIPS, and the fixed-point arithmetic units have been used for lower power consumption since they consume less power than floating point units [2].…”

Design and Implementation of an Arithmetic Processor Unit Based on the Logarithmic Number System

“…Debido a que el LNS basa su funcionamiento en las propiedades de las funciones logaritmo y antilogaritmo, este sistema numérico permite realizar operaciones de multiplicación, división y raíz cuadrada haciendo uso de sumas, restas y desplazamientos lógicos en el formato de punto fijo, reduciendo de esta forma la complejidad de la arquitectura hardware de dichas operaciones [2], [3].…”