Masked Data Bit Selection Circuit for Graphics Memory Power Reduction
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Solution Overview
Problem
In graphics memory systems, unused masked data bits during write operations lead to wastage of signaling power and contribute to simultaneously switching output (SSO) noise, which limits data rate and increases power consumption.
Innovation Solution
A selection circuit in the graphics controller uses a data mask signal to drive alternative values on data lines during write operations, minimizing power consumption and reducing SSO noise by either using high-voltage values for PODL terminations or transmitting previous values for unterminated data lines, and employing an alternative-value-generation circuit to limit high-voltage values and communicate calibration or side-band data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If masked data bits are transmitted during write operations, then data integrity is maintained, but signaling power consumption increases and SSO noise is generated
Solution Approach 1:
The patent applies local quality by treating masked and unmasked data bits differently. For masked bits, alternative values (0, 1, or previous values) are driven based on local conditions (mask signal assertion), while unmasked bits continue normal operation. This localized differentiation reduces power consumption and SSO noise for masked bits without affecting the integrity of unmasked data transmission.
Solution Approach 2:
The patent changes the parameter being driven on data lines for masked bits from the original data value to alternative values (0, 1, or previous transmitted values). This parameter change is controlled by the mask signal and reduces the switching activity on data lines, thereby reducing signaling power consumption and minimizing SSO noise generation.
2Loss of energy
If alternative values are driven for masked data bits, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The patent segments the data bit handling into two paths: masked bits that receive alternative values and unmasked bits that transmit normal data. This segmentation is achieved through the mask signal controlling the selection circuit, allowing independent optimization of power consumption for masked bits while maintaining normal operation for unmasked bits.
Solution Approach 2:
The selection circuit automatically selects appropriate alternative values (0, 1, or previous values) based on the mask signal assertion without requiring external intervention. The circuit serves itself by internally managing the alternative value selection and driving, reducing the need for additional control logic and minimizing device complexity.
3Loss of energy
If high-voltage values are used for PODL terminations, then signaling power is minimized, but data rate may be limited
Solution Approach 1:
The patent employs periodic action by alternating between driving 0, 1, or previous values for masked bits based on the mask signal and data pattern. This periodic variation in driving strategy allows the system to minimize power consumption during masked bit transmission while maintaining acceptable data rates through the use of previous values that reduce switching activity.
Data Source
AI summary
Embodiments of an apparatus that uses unused masked data bits during an access to a memory are described. This apparatus includes a selection circuit, which selects data bits to be driven on data lines during the access to the memory. This selection circuit includes a control input that receives a data mask signal, which indicates whether a set of data bits is to be masked during the access to the memory. During the access to the memory, the selection circuit selects either the set of data bits to be driven when the data mask signal is not asserted, or an alternative set of values to be driven when the data mask signal is asserted.