With the high speeds and fast edges, we can't tolerate the effects of long leads or even large lead frames as we did when clocks were at about 10 or 12 MHz. Further, the greater use of totally synchronous logic requires that more emphasis be put on short distance between power pins and supply bypass members. Keeping 'em a mm or so is not unreasonable. Having a 20 mm lead frame doesn't help anything in that regard. As much as I like working with the generously spaced leads on the old-style DIL packages, Even I have learned to use PLCC's for wire-wrap and whatever adapters are suitable for other packages, e.g. TQFP.

However, it's no secret that few applications really require those ultra-fast MCU's. If a 12 MHz 12-clocker will do the job, there's little, though some, advantage in using a slower one-clocker, though it does save power.

RE


RE