Semiconductor Memory Segmentation for Boot Speed and Power
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Solution Overview
Problem
The boot time of processors is significantly prolonged due to the slower reading speed of nonvolatile memories, especially when power consumption is reduced through power gating, resulting in a diminished effect on power savings.
Innovation Solution
A semiconductor device with a memory circuit comprising a first memory region for storing the start-up routine and a second memory region for normal operation, utilizing oxide semiconductors in transistors and capacitors with varying storage capacitance and channel length-to-width ratios to enhance data retention and access speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nonvolatile memory is used to store start-up routine to reduce power consumption, then power consumption is reduced, but boot time is significantly prolonged
Solution Approach 1:
The memory system is segmented into two distinct regions: a first memory region with high data retention characteristics for storing critical start-up routines and initial values, and a second memory region with high read speed for fast data access. This segmentation allows each region to be optimized for its specific function, resolving the contradiction between power consumption and boot time.
Solution Approach 2:
Different memory regions are assigned different characteristics tailored to their specific needs. The first memory region uses oxide semiconductor transistors with larger L/W ratios for superior data retention, while the second memory region uses transistors with smaller L/W ratios for faster read operations. This local quality differentiation enables simultaneous optimization of both power efficiency and speed.
2Use of energy by moving object
If power gating is used to reduce power consumption, then power consumption is reduced, but processor reboot time is prolonged
Solution Approach 1:
The start-up routine and essential initial values are pre-stored in the first memory region with high data retention characteristics. This preliminary action ensures that when power gating is applied and the processor needs to reboot, the critical data is already in place and can be quickly accessed, significantly reducing reboot time while maintaining power savings.
Solution Approach 2:
The first memory region acts as an intermediary between the power gating mechanism and the processor. It retains critical data during power-off periods and provides it quickly during reboot, mediating between the power-saving state and the active processing state to enable fast recovery.
3Reliability
If oxide semiconductor transistors with larger L/W ratio are used in first memory region, then data retention is improved, but transistor area increases
Solution Approach 1:
The memory system is divided into two regions with different transistor specifications. The first memory region uses oxide semiconductor transistors with larger L/W ratios optimized for data retention, while the second memory region uses transistors with smaller L/W ratios optimized for speed. This segmentation allows each region to achieve its performance goals without unnecessarily increasing overall area.
Solution Approach 2:
Larger L/W ratio transistors are deployed only in the first memory region where data retention is critical, rather than uniformly across the entire memory system. This local quality approach ensures high reliability where needed while minimizing the area impact on the overall device.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for rapid booting and rebooting of processors during frequent power gating while reducing power consumption by optimizing memory access and retention characteristics.
Implementation Method 1
the first transistor and the second transistor each include an oxide semiconductor in a channel formation region
Implementation Method 2
the first capacitor has a larger storage capacitance than the second capacitor
Data Source
AI summary
The operation speed of a semiconductor device is improved. The semiconductor device includes a first memory region and a second memory region; in the semiconductor device, a first memory cell in the first memory region is superior to a second memory cell in the second memory region in data retention characteristics such as a large storage capacitance or a large channel length-channel width ratio (L/W) of a transistor. When the semiconductor device is used as a cache memory or a main memory device of a processor, the first memory region mainly stores a start-up routine and is not used as a work region for arithmetic operation, and the second memory region is used as a work region for arithmetic operation. The first memory region becomes an accessible region when the processor is booted, and the first memory region becomes an inaccessible region when the processor is in normal operation.