Navigating the Seismic Shift of Post-Moore Computer Systems Design

Reports on the history and development of computer aided design systems. In quick succession between 1964 and 1971, our field saw the proposal of Moore's law,1 the coining of the term computer architecture,2 and the introduction of the first microprocessor.3 For much of the five decades since then, we have benefitted extraordinarily from both the dynamism of Moore's law transistor scaling and the stable durability of the hardware-software abstractions of computer architecture. The dynamic duo of Moore's law and computer architecture have allowed massive scaling to occur, and also to be navigated smoothly with relatively little software impact. For example, in the late 1980s and early 1990s, surges in power density occurred as we reached challenging limits in very large scale integration (VLSI) designs based on bipolar transistors; a technology transition from bipolar to complementary metal-oxide-semiconductor (CMOS) occurred with relatively little impact or awareness from the software portion of the computing community.4 Over the past 10-15 years however, more fundamental shifts have occurred. For example, Dennard scaling,5 a companion phenomenon to Moore's law stating that power density could remain stable while transistor sizes shrank, is reaching physical limits. This means that further Moore's law increases in transistor counts are becoming more complex and are only achieved with great effort and at higher power-density costs. Furthermore, as we reach fundamental physical limits in the functioning of small semiconductor transistors, Moore's law itself is being challenged by the increased physical effort and financial expense required to maintain transistor scaling trends.