Memory power reduction

 *  Memory retention voltage depends on PVT

  * Leakage during memory state retention ( Data retention during standby) 

* As retention time increases more errors 

 

Solutions: 

1. Voltage scaling ( as VDD reduces number of errors increases , Leakage current ) 

2. Error correction codes 

Effect of ECC: 

1. max 1 error per line can be corrected, 2 errors can be detected 

2. Area: Memory size increase by (n-k)/n 

  small additional area for encoder and decoder units ( Fully combinational blocks) 

3. Latency : Encoding latency added to write access 

                    Decoding latency added to read access 

For SEC/SED 

Number of data bits    No of check bits

8-11                                  5

12-26                                6

27-57                                7

58- 120                              8

-> Enable/Disable ECC?