What does the “D” mean? The “D” doesn’t stand for anything. It is merely a way of distinguishing the current generation of Celerons from past generations. The Celeron and Celeron D are two totally different CPUs. The Celeron uses the Northwood core built on 130nm, and has 128k L2 cache. The default FSB is 100 MHz. The Celeron D uses the newer, but not always better, Prescott core built on 90nm, and has 256k L2 cache. The default FSB is slightly higher at 133 MHz.