FPBA：基于百分位数的灵活分配适用于每单元多位 RRAM.pdf

1、Junfei Liu and Anson Kahng University of RochesterFPBA:Flexible Percentile-Based Allocation for Multiple-Bits-Per-Cell RRAMResistive Random Access Memory(RRAM)Non-volatile memory technology Stores data by changing resistance with voltage Resistance value set at write operation(“write center”)Smaller

2、 voltage used to measure the resistance multiple times to characterize the resistance distribution Allows for multiple-bits-per-cell(MBPC)Central question:How to partition MBPC RRAM cells into non-overlapping levels with low error?Level allocation algorithm:Map bit combinations to resistance ranges

3、Write center,read range Data corruption:Write to level 3(“11”),read from level 4(“10”)one bit flip cxl,xhMultiple-Bit-Per-Cell(MBPC)Level AllocationWei et al.“PBA:Percentile-Based Level Allocation for Multiple-Bits-Per-Cell RRAM”.ICCAD 2023.Error probability():Maximum allowable probability of a bit

4、error of an allocated level Example:=2%with a level (inclusive),(exclusive)xl=7xl=18Core ConceptsGray coding:Encoding that ensures one bit flip between adjacent levels Bit error rate(BER):Error-correcting code overhead(ECC):Fraction of additional bits needed to protect against errors(Reed-Solomon,BC

5、H,or Hamming encoding)related to BERNumberofbitflipsTotalbits 100%Core ConceptsResistance stateGray-coded bit valueR1(highest)“00”R2“01”R3“11”R4(lowest)“10”Minimize during level allocation Minimize BER and ECC overhead in the end Overall flow:ObjectivesFind levels with minimum Level encodingRaw BERE

6、CC overheadLevel allocationSigma-Based Allocation(SBA)1:Fit distributions to characterization data Parameterization not always applicable Percentile-Based Allocation(PBA)2:State-of-the-art Directly work with characterization data Capture analog behaviors present in the data Great improvement over SB