Sorry about the mud, guys. Now "bygones." Re: Larry's comments on high frequency energy making it to the board and causing EMI problems, this is and has been a major issue with all higher frequency processors. The 200 MHz limit that (to quote Larry) "some one" specified is constantly violated by processors. The original (pre-production) AMD K6 processor packages (prototyped by IBM, certainly a competent manufacturer) exhibited a package resonance at 750 MHz that (per the mode conversion phenomenon aptly noted by Scott McMorrow) leaked (or actually ran rampant) onto the PCB and was very nicely characterized by EMI radiated emission tests. This problem was measured, characterized, modeled, and correctly simulated for an indepth understanding. Multiple in-package filter alterations were modeled and evaluated that offered attenuation exceeding 60 dB. But power carrying ability of the resulting structure posed lower practical limits to lower levels (as noted by Larry). And, as most of us know, on-die decoupling capacitance goes a long way to reducing the resonant frequency and containing the higher frequency currents on the chip. My (years ago) analyses of this problem clearly demonstrated the need (and the potential) for innovative package design that is still an ongoing issue for all processor manufacturers. Grounded heatsinks on these chips have provided a field interseptor and shielding improvement for some of the energy, but thin dielectric planar decoupling is a critical element on the PCB to resolving EMI problems beyond the control of the processor package designer. Mike Michael L. Conn Owner/Principal Consultant Mikon Consulting Cell: (408)821-9843 *** Serving Your Needs with Technical Excellence *** ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu