We all know that the rate of improvement in microprocessor speed exceeds the rate of improvement in DRAM memory speed - each is improving exponentially, but the exponent for microprocessors is substantially larger than that for DRAMs. The difference between diverging exponentials also grows exponentially; so, although the disparity between processor and memory speed is already an issue, downstream someplace it will be a much bigger one.
According to an article in IEEE spectrum that time is almost upon us. With cores per processor doubling every 2-3 years - and graphics chips moving faster - we don't have long to wait.
The memory wall's impact is greatest on so-called informatics applications, where massive amounts of data must be processed. Like sifting through petabytes of remote sensing data to find bad guys with nukes.
Can this be fixed?
Sandia is investigating stacked memory architectures, popular in cell phones for space reasons, to get more memory bandwidth. But as the simulation shows, that doesn't improve performance.