@Alvie "This is the first part of the artice. The second part will deal with adding an extra write port to the design"
Hopefully I haven't disrupted the natural order of the blog series in replying to Karl's post ( which I might have misunderstood anyway ).
Perhaps not obvious from my original post here, but the intent of the earlier APP link was to cover some practical issues ( synthesis directives & coding styles ) needed to successfully infer a "replicated" multiport structure with Synplify in an FPGA target having only Simple Dual Port RAM.
@Brian: This is not the same as using 2 simple dual ports. There both RAMs must be written every time to maintain integrity.
In this case is special because true dual port can write one port and read a different address simultaneously on the other port. The write to the second port is a write thru only if the addresses are the same.
Therewfore I think there is no way to make a true dual port using 2 simple dual ports because for writes both addresses have to be the same.