A mismatch-dependent power allocation technique for match-line sensing in content-addressable memories

Abstract

In the conventional content-addressable memory (CAM), equal power is consumed to determine if a stored word is matched to a search word or mismatched, independent of the number of mismatched bits. This paper presents a match-line (ML) sensing scheme that allocates less power to match decisions involving a larger number of mismatched bits. Since the majority of CAM words are mismatched, this scheme results in a significant CAM power reduction. The proposed ML sensing scheme is implemented in a 256 144-bit ternary CAM for a 0.13-m 1.2-V CMOS logic process. For a 2-ns search time on a 144-bit word, the proposed scheme saves 60% of the power consumed by the conventional sensing scheme.Index Terms-Associative memory, content-addressable memory (CAM), current sensing, high speed, low power, match-line sensing, mismatch dependent, neural network, pattern matching, string matching.

Low-Power Ternary Content-Addressable Memory Using Power Reduction of Match-Line and Search-Line

“…The NAND type cell has the advantage of less power consumption than the NOR type because the ML of the cell is connected in series. However, as TCAM size increases, there is a disadvantage that an unacceptably long search time is required [20]. In addition, NOR-type is preferred over NAND-type because of the less susceptibility to failure due to the variation of process, temperature and supply voltage [21].…”

Performance Comparison of Positive Feedback Match-Line (ML) Sensing Schemes for Low Power TCAM

“…3) is included to monitor the voltage development on an ML and accordingly reduce the charging current as it becomes evident with time if an ML is mismatched [15]. The mismatch dependent (MD) MLSA in [15] suffers from the problem that, when idle, there is a dc path from Vdd to ground causing static power consumption. Circuit diagram for this scheme in shown in Fig.…”

“…4. Circuit level implementation of mismatch dependent ML sensing scheme [15] B. Active Feedback Scheme In order to reduce the energy consumption and delay without sacrificing the voltage margin, there is another positive feedback based ML sensing scheme called active feedback.…”

Networking Application of CAM with Improved Process Variation Tolerance Using Paritybits and MLSA

“…A small model is shown in Figure1.It consist of core cells,searchline ,matchline, MLSA and an encoder. Searchdata register is used to get the input from the user,and then it will be compared with the memory bank through search line.Matchline sensing amplifiers are used to sense the voltage variations from the matchline.Encoder is used to identify the location of the output [2]. …”

“…A CAM cell serves two basic functions: bit storage (as inRAM) and bit comparison (unique to CAM).There are three types of core cells are used such as NAND cell ,NOR cell and Hyprid type cell [2].…”