Advanced Microarchitecture and Circuit Design Techniques
for On-Chip Memories in CMOS Technology
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1. INTRODUCTION
1.1. Microelectronics Evolution
Over the past 60 years, the evolution of the microelectronics industry has undergone extraordinary developments. In December 1947, Bell Laboratories® constructed the first point-contact transistor (Figure 1.1(a)), consisting of a block of germanium with two gold contacts. These gold contacts were spaced only a few thousandths of an inch apart and were supported by a wedge-shaped insulating material [1.1]. This was the first type of solid-state electronic transistor, replacing the vacuum tube. In 1971, Intel® developed the first microprocessor called the 4004 (Figure 1.2(a)), primarily targeted for use in calculators [1.2].


Microprocessor Overview
The microprocessor optimization space, from top to bottom, includes software, platform, architecture, logic, circuits, and process (Figure 1.3). All levels have varying degrees of design optimization space for performance, power, area, and robustness.



Register Files
Multi-ported register files are basic building blocks in superscalar microprocessors since they enable concurrent execution of multiple instructions during one cycle. The architecture of the register file consists of a decode block and array block (Figure 1.12). The size of the register file varies depending on the number of entries, bits, and read/write ports. Since the number of read/write ports vary, there is a separate decode block to determine the specific location corresponding to the input address. A read/write N-wide address bit scales to a maximum of 2N number of entries and stores M-wide data for each entry. Therefore, the total number of bits stored would MxN.


Thesis Contribution and Organization
This thesis proposes microarchitecture and circuit techniques that aim to improve the trade-offs between performance, power, area, and robustness for on-chip memories. These techniques address the improvement of one of the most important on-chip memories in a superscalar microprocessor -- large-signal multi-ported register files.