I just checked Chris Smith's book "The ZX Spectrum ULA" and it says page mode is used: the video system fetches pixel data and attribute data from the same DRAM column. As you suggest, this saves time. (Not sure why your title says "Before page-mode" - perhaps you could clarify?)
So page mode should be very useful for sequential accesses, at the cost of some complexity. It seems that the 68000 doesn't have that complexity - it makes a full row and column access every time, according to
http://patpend.net/technical/68000/68000faq.txtEven with the 68020 it seems an external memory controller would be needed to arrange for so-called burst accesses - see
http://www.textfiles.com/bitsavers/pdf/ ... N-0616.pdfIt's not so easy to create the optimum strobe timings though: the Spectrum uses both edges of the 7MHz clock and still needs to use gate delays to shift edges - that's a technique to be used only with great care, because the delays will vary across different devices, and voltage and temperature.
Edit: Acorn's Electron uses just 4 DRAMs and so every byte access requires two DRAM accesses - I imagine it uses page mode every time, for each pair. I don't know if it's any more aggressive when doing video refresh, but it probably could be. (If it happens that a scan line can be configured to start on any address, which I imagine a 6845 would allow, that makes it much harder and much less likely. But any alignment constraint on a scan line would allow for page mode accesses. I don't know much about the Electron's video configuration flexibility.)
The best possible result would be a doubling of memory throughput, I think. See
http://en.wikipedia.org/wiki/Dynamic_ra ... ess_memory