Pulsed silicon double-drift IMPATT diodes that yield 42 W at 96 GHz are discussed. Owing to the considerable input powers (about 500 W), these diodes are mounted on diamond heat sinks. Because of the strong carrier injection, the field distribution in the diode is similar to that in a p-i-n diode. An attempt is made to explain the results using Misawa's (1966) p-i-n type theory. The large-signal avalanche resonant frequency is close to the operation frequency. Conventional Read-type theory fails to explain these results because of the current densities employed in the experiments.