Often in the hurry to create the future, computer engineers ignore lessons from past projects. One project that offers interesting insights, the IBM System/360 Model 91, recently celebrated the 30th anniversary of its first shipment. The largest member of the series based on IBM?s most enduring and influential computer architecture, this machine owed much to its predecessors. Together, these machines show us what the state of the art in computer processors was like in the 1960s and illustrate how far computer engineering has come in 30 years. By looking back, can computer engineers learn what needs to change for the future? In the future, every computer engineer should use existing publications and source material. Perhaps most importantly, computer engineers need to acknowledge the use of prior references. The author thinks it depressing to see engineers waste work rediscovering an old idea. He finds it even more discouraging to see them use old ideas without acknowledgment when the idea?s source is obvious.