I've tried to do a such thing with a COP8 (National).
I get a chip from an old memory for 8086 (1bit * 1Mbit).
The problem is the refresh (obviously ... )
I would to use timer of COP8 to refresh DRAM with no µC overhead. I think it's possible but I have not tried that.
In fact, I begin with an IT that refresh some column of DRAM (2 or 3 for example). The overhead is minimum in this case.
It seems to work very good. In fact I can refresh the DRAM 10 time slower than nominal rate and it work ...
It's a bit strange ...
Another point is that it is a 1bit memory and the column and line adresses are multiplexed. So to put or get one byte, there are a lot of cycles ...
But I don't do a lot more, I have used that for getting CD-TEXT from a CD (and it work I get 1ko of text -- the same amount of data that the eniere COP8 contain) ... but the CD-ROM Player (Sony) died very few time after that ...
And I replaced it with another CD-ROM Player, but it can't retrieve CD-TEXT, so I have don't go further.
(Sorry for poor English)