This paper discusses display designs which store the image point by point in random access memory, so that independent update of every pixel is possible. A frequent bottleneck in the design of high performance displays of this type is the available bandwidth of the memory subsystem. In this paper, we focus on this issue and present features of a customized dynamic RAM chip which can readily provide the necessary bandwidth and thus greatly simplify the design of very high performance APA raster scan displays. The customized RAM chip is quasi-two-ported. After briefly introducing APA raster displays, we discuss display memory system design and the design of the proposed custom memory chip. We describe the second port for the video refresh, which makes the primary port available for update almost continuously. We also discuss modifications to the existing primary port to make it easily usable for the parallel update required for high update performance as well as for other applications.