Table 5.8 is the optical memory counterpart to Table 5.7, which was for optical interconnects. It will not be a technological challenge to provide sufficient memory capacity for PetaFLOPS systems, but research is needed to improve access times for optical memories. With respect to CD ROMs, this may be accomplished by employing multiple read-heads placed strategically around the disk. No matter what the storage technology, increased access time goes along with increased capacity. But the advantage of optical memory is that it lends itself well to parallel addressing due to the ability to image data from the memory; therefore, once the desired data field has been accessed, the data readout rates can be extremely high. This implies that optical memories may be well suited to PetaFLOPS computers designed to work with large two-dimensional data fields, such as images and other multidimensional signals.
Table 5.8 indicates places within the PetaFLOPS computer hierarchy where various optical memory technologies will likely be needed for each of the three proposed PetaFLOPS architectures.
