According to https://en.wikipedia.org/wiki/Dynamic_random-access_memory#Page_mode_DRAM
Page mode DRAM is a minor modification to the first-generation DRAM IC interface which improved the performance of reads and writes to a row by avoiding the inefficiency of precharging and opening the same row repeatedly to access a different column.
Minor in implementation difficulty, but major in performance implication; faster multiword data transfer can substantially speed up many operations.
When did CPUs start being able to make use of this? The instruction timing tables I've seen for seventies and early eighties CPUs such as the 6502, Z80 and 68000 suggest they did not use page mode. On the other hand, I've found a few PDFs that indicate the 68030 did. I haven't been able to find anything definite on the 68020. (Apparently the video chip on the Sinclair Spectrum did use it, so even if the CPU didn't, the capability didn't go to waste.)