A reconfigurable multilevel parallel texture cache memory with 75-GB/s parallel cache replacement bandwidth

Abstract

Recently, the level of realism in PC graphics applications has been approaching that of high-end graphics workstations, necessitating a more sophisticated texture data cache memory to overcome the finite bandwidth of the AGP or PCI bus. This paper proposes a multilevel parallel texture cache memory to reduce the required data bandwidth on the AGP or PCI bus and to accelerate the operations of parallel graphics pipelines in PC graphics cards. The proposed cache memory is fabricated by 0.16-m DRAM-based SOC technology. It is composed of four components: an 8-MB DRAM L2 cache, 8-way parallel SRAM L1 caches, pipelined texture data filters, and a serial-to-parallel loader. For high-speed parallel L1 cache data replacement, the internal bus bandwidth has been maximized up to 75 GB/s with a newly proposed hidden double data transfer scheme. In addition, the cache memory has a reconfigurable architecture in its line size for optimal caching performance in various graphics applications from three-dimensional (3-D) games to high-quality 3-D movies. This architecture also leads to optimal power consumption with an adaptive sub-wordline activation scheme. The pipelined texture data filters and the dedicated structure of the L1 caches implemented by the DRAM peripheral transistors show the potential of DRAM-based SOC design with better performance-to-cost ratio. Index Terms-3-D graphics, DRAM-based SOC, DRAM L2 cache, multilevel parallel cache, texture cache. I. INTRODUCTION A S THREE-DIMENSIONAL (3-D) graphics become one of the most important components of multimedia applications today, 3-D graphics processing power has become a major performance index of multimedia systems, such as PCs or portable information terminals [1]-[5]. At present, the level of realism of PC graphics scenes is comparable to that of high-end graphics workstations a few years ago [6], [7]. For the generation of realistic scenes, texture mapping has been frequently used in 3-D graphics [8]. This technique enhances the realism of 3-D graphics scenes by wrapping 3-D model surfaces with two-dimensional (2-D) texture images obtained by scanning the surface of the 3-D objects in real space. By the texture mapping operation, surface details such as color and roughness can easily