I just took Howard Johnson's class on high speed digital design- which I have to say was a *great* class. If you can't take his class, look for his book: _High Speed Digital Design_ (A handbook of black magic), Howard Johnson and Martin Graham, ISBN: 0-13-395724-1. High speed design for him starts at 20 MHz. In his book and class he has collected a lot of the old rules of thumb, debunks a few, but gives reasons for them all. (example- right angle traces on PCBs- we've been told they are the ultimate no-no in PCB design for years. He explains what is actually going wrong and how it actually effects your circuit [not much]). His website is . He's a darned good public speaker too. What made me connect this thread to his class was this thought on protoboards- yes, they have a lot of capacitance, but in addition, especially for high speed design, they promote bad techniques, such as wires too long, leads too long, and so forth. He had a particularly good demo on lead length and how it affects inductance of parts. What was incredible was how much a capacitor with long leads is not a capacitor for a brief bit of time. What is particularly scary is that with a slow scope, you'll never see these effects, even though they may be fast enough to affect your circuit. A few pF here, a few nH there, they add up. With protoboards you have to take some extra care in the construction of your circuit and the selection of your parts. Think again about using that really fast, low impedance gate- the fast edges could cause all sorts of problems you'll never see with a 100 MHz scope. Protoboards are good tools, but like any tool, you need to understand when its use is appropriate. Matt Bennett -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.