General information

Embedded systems invade our daily life in a a generally invisible manner and represent the largest part of computing systems in the world. Many common embedded systems have to be electrically autonomous: cellular phones, digital cameras, etc. In such systems, electricity usage — power and above all energy — is of course an important issue. Indeed, in spite of advances in batteries many systems remain highly constrained by available energy and have an autonomy that is still too limited. In addition, on the other side of the spectrum of systems, that is to say in supercomputers or in a grid of computers, energy related issues become more and more important. In such system, although autonomy is not an issue, total energy usage soars and implies a significant cost. Energy savings can thus have a strong ecological and economical impact. Instantaneous power usage is also an issue since it incurs cumbersome and expensive power supply devices. It also strongly influences the temperature of circuits, whose overheating is harmful for their reliability, and thus imposes using colling solutions that are cumbersome too, as well as expensive to buy and operate. Reducing instantaneous power thus offers numerous practical, economical and ecological advantages. Internship topic In the above context, forecasts hinted that memory could account for as much as 70 to 90 % of the tota