What is the difference between 2K and 4K refresh and can SIMCHECK II support these refresh varieties?
A. The DRAM memory array is arranged along a matrix of Rows and Columns. Each memory cell is accessed by multiplexing first the Row address and then the Column address. The row is the main access, and all the cells in a row are refreshed when the row is accessed. When the number of rows is equal to the number of columns, we say that the DRAM is symmetric, when the rows number is different than the columns number, we say that the DRAM is asymmetric. Asymmetric DRAM has the advantage of reduced power consumption, as less refresh is required. A symmetric 4M device with 11 address lines for both rows and columns has 2K refresh. An asymmetric 4M device with 12 rows and only 10 columns is called 4K refresh. SIMCHECK II automatically detects the refresh type (1K, 2K, 4K and the new 8K). Since historically symmetric devices were first used, SIMCHECK II regards symmetric devices as default, and puts a structure note message when an asymmetric device is encountered.
