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The DDR4 specification defines 1x, 2x and 4x refresh modes as follows:

The default Refresh rate mode is fixed 1x mode where Refresh commands should be issued with the normal rate, i.e., tREFI1 = tREFI(base) (for Tcase<=85°C), and the duration of each refresh command is the normal refresh cycle time (tRFC1). In 2x mode (either fixed 2x or on-the-fly 2x mode), Refresh commands should be issued to the DRAM at the double frequency (tREFI2 = tREFI(base)/2) of the normal Refresh rate. In 4x mode, Refresh command rate should be quadrupled (tREFI4 = tREFI(base)/4). Per each mode and command type, tRFC parameter has different values as defined in Table 23.

I was expecting the refresh modes to correspond to different temperature ranges but that does not seem to be the case as shown in the Micron datasheet excerpt below (it seems you could use 4X mode in the normal, 0°C <= Tcase <= 85°C, range):

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So what's the purpose of those 1X, 2X and 4X refresh modes?

geschema
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    https://docs.xilinx.com/r/en-US/pg313-network-on-chip/LPDDR4-Refresh-Options show the benefits of these modes. – shparekh Jun 08 '23 at 22:37

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