CACTI: an enhanced cache access and cycle time model

TLDR

The paper presents an analytical model for estimating access and cycle times of on‑chip direct‑mapped and set‑associative caches. The model takes cache size, block size, associativity, array organization, and process parameters as inputs, and extends prior work by adding detailed components such as tag array, comparator, multiplexor drivers, non‑step stage input slopes, rectangular stacking of memory subarrays, a transistor‑level decoder, column‑multiplexed bitlines, load‑dependent size transistors for wordline drivers, and outputs both cycle and access times. The model’s estimates are within 6 % of Hspice results for selected circuits, and the accompanying software is available via FTP.

Abstract

This paper describes an analytical model for the access and cycle times of on-chip direct-mapped and set-associative caches. The inputs to the model are the cache size, block size, and associativity, as well as array organization and process parameters. The model gives estimates that are within 6% of Hspice results for the circuits we have chosen. This model extends previous models and fixes many of their major shortcomings. New features include models for the tag array, comparator, and multiplexor drivers, nonstep stage input slopes, rectangular stacking of memory subarrays, a transistor-level decoder model, column-multiplexed bitlines controlled by an additional array organizational parameter, load-dependent size transistors for wordline drivers, and output of cycle times as well as access times. Software implementing the model is available via ftp.