Random Number Generator Using Rotator for DRAM Row Hammer Mitigation
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Solution Overview
Problem
In miniaturized DRAM devices, the row hammer effect causes bit flips due to charge leakage between adjacent memory devices, leading to error signals, which existing refresh operations and random number generators struggle to effectively mitigate.
Innovation Solution
A random number generator comprising a linear feedback shift register and a rotator that generates pseudo-random number sequences by shifting and rotating binary codes based on control and pulse signals, creating distinct sequences to address the row hammer effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If memory devices are miniaturized and placed closer together to increase density, then productivity and memory capacity are improved, but the row hammer effect occurs causing bit flips and errors
Solution Approach 1:
The system performs preliminary actions by generating random refresh patterns before bit flips can occur. The linear feedback shift register continuously generates pseudo-random sequences that are used to selectively refresh memory rows, preventing charge leakage from causing bit flips in the first place rather than correcting errors after they occur.
Solution Approach 2:
The linear feedback shift register uses feedback connections where the output of the register is fed back to the input through XOR gates, creating a continuous pseudo-random sequence generation mechanism. This feedback mechanism ensures the generation of non-repeating refresh patterns that effectively mitigate the row hammer effect while maintaining system reliability.
2Reliability
If conventional random number generators are used for refresh operations, then bit flip mitigation is achieved, but the random sequences can be predicted and are not sufficiently random
Solution Approach 1:
The system introduces dynamics by continuously changing the refresh patterns through pseudo-random sequences generated by the linear feedback shift register. The rotator component dynamically adjusts the sequence values by rotating bits, ensuring that refresh patterns are constantly varying and unpredictable, thereby preventing the row hammer effect while maintaining high randomness quality.
Solution Approach 2:
The rotator component adds another dimension to the random sequence generation by performing bit rotation operations on the sequences generated by the linear feedback shift register. This dimensional transformation enhances the randomness by transforming the original sequences into new sequences with different statistical properties, making prediction even more difficult.
3Loss of information
If random number generation complexity is increased to improve randomness quality, then unpredictability is improved, but device complexity increases
Solution Approach 1:
The linear feedback shift register serves multiple functions: it generates pseudo-random sequences, provides timing signals, and can be configured with different feedback polynomials to generate different sequences. The rotator component also serves dual purposes by both rotating bits to enhance randomness and controlling the sequence generation process, thereby reducing overall device complexity while maintaining high randomness quality.
Data Source
AI summary
A random number generator is provided. The random number generator includes a linear feedback shift register and rotator. The linear feedback shift register is configured to provide a first pseudo-random number signal with a first value, wherein the first pseudo-random number signal includes a plurality of bits. The rotator is configured to shift and rotate the plurality of bits of the first pseudo-random number signal according to a signal to generate a second pseudo-random number signal with a second value. The second value is different from the first value.