More Chips Means Less Salsa

Yes, I just got through watching the Superbowl so chips and salsa are on my mind and in my stomach. In recreational eating more chips requires downing more salsa. With mulitcore chips it turns out as cores go up salsa goes down, salsa obviously being a metaphor for speed.

Sandia National Laboratories found in their simulations: a significant increase in speed going from two to four multicores, but an insignificant increase from four to eight multicores. Exceeding eight multicores causes a decrease in speed. Sixteen multicores perform barely as well as two, and after that, a steep decline is registered as more cores are added. The problem is the lack of memory bandwidth as well as contention between processors over the memory bus available to each processor.

The implication for those following a diagonal scaling strategy is to work like heck to make your system fit within eight multicores. After that you'll need to consider some sort of partitioning strategy. What's interesting is the research on where the cutoff point will be.