應用於無線影像娛樂系統的隨選記憶體系統

Abstract

隨著人們對於無所不在的無線高速資料傳輸多媒體影音需求逐年增加，邁向多核心、多執行及多系統融合平台才有辦法達到未來的需求。然而，多核心平台需要一個的記憶體系統來提供足夠的資料頻寬以及良好的記憶體管理機制。在本論文中，我們提出了適合於多核心平台的高效能、低功率隨選記憶體系統。並將其應用在無線影像娛樂系統上。 在所提出的隨選記憶體系統中，主要包含了分散式記憶體管理器以及集中式記憶體管理器。在分散式記憶體管理器中，我們提出了一個借取 (borrowing)機制，此機制可以動態地分配記憶體資源給晶內網路封包的暫存使用，以減少處理單元暫停的情況。而在集中式記憶體管理器中，所提出的適應性快取控制機制可以根據不同處理單元的記憶體存取特性來分配不一樣記憶體資源。此外，在集中式記憶體管理器中也建構了一個外部記憶體存取介面來有效地存取晶外記憶體。另外，針對應用於無線影像娛樂系統上的可階式視訊編碼(Scalable Video Coding)，我們提出了預取(pre-fetch)資料的機制和有效率的動態記憶體(DRAM)資料安排的機制來減少快取記憶體的失誤率以及動態記憶體的能源消耗。並利用在集中式記憶體中的適應性快取控制，可讓系統達到最佳的記憶體使用率。

With increasing demands on ubiquitous wireless high-data-rate multimedia services, it is critical to have efficient processing capability and a merging multi-task system to sustain the growth. Therefore, a well-organized memory system can provide enough bandwidth and optimize memory managements. In this thesis, an on-demand memory system is presented to overcome the challenges in the multi-task and heterogeneous multi-core system design. The proposed on-demand memory system, consisting of distributed and centralized memory management units (MMUs), provides energy-efficient memory-centric on-chip data communication for wireless video entertainment systems.

Distributed MMUs (d-MMUs) can dynamically allocate the memory resource for network data buffering to reduce the stall of processor elements based on the proposed borrowing mechanism. Furthermore, the c-MMU manages centralized on-chip memories (L2 cache) and off-chip memories. For different memory requirement of the processor elements in the system, adaptive memory resource allocation is applied via the proposed adaptive cache control. Additionally, in order to access off-chip DRAM efficiently, an external memory interface is designed in c-MMU. By considering the characteristics of the wireless video data, an inter-layer pre-fetch mechanism and an efficient data allocation scheme are proposed to reduce the cache miss rate and memory energy consumptions for Scalable Video Coding (SVC).