A Large, Fast Instruction Window for Tolerating Cache Misses

Instruction window size is an important design parameter for many modern processors. Large instruction windows offer the potential advantage of exposing large amounts of instruction level parallelism. Unfortunately, naively scaling conventional window designs can significantly degrade clock cycle time, undermining the benefits of increased parallelism. This paper presents a new instruction window design targeted at achieving the latency tolerance of large windows with the clock cycle time of small windows. The key observation is that instructions dependent on a long latency operation (e.g., cache miss) cannot execute until that source operation completes. These instructions are moved out of the conventional, small, issue queue to a much larger waiting instruction buffer (WIB). When the long latency operation completes, the instructions are reinserted into the issue queue. In this paper, we focus specifically on load cache misses and their dependent instructions. Simulations reveal ...

• Type: Conference
• Year: 2002
• Where: ISCA
• Authors: Alvin R. Lebeck, Tong Li, Eric Rotenberg, Jinson Koppanalil, Jaidev P. Patwardhan
• Keywords: Clock Cycle Time, Hardware, Instruction Window, ISCA 2002, Issue Queue