< > terminator. Do all S-100 buses require external termination, or did m < Only the motherboards that didn't have active termination require a < terminator. In my experience, that's a fair number of mobo's out there My experience with 4 or 5 crates I have and many I've built up. If it runs well or the bus looks clean to the O'scope skip it. Some busses it's helps but still look terrible (altair with the original backplanes). My Northstar Horizon never needed one and it's currently running at 8mhz. The VectorMX box I have with Compupro backplane needed the terminators installed for 10mhz. The CCS I'm using with discus hard disk and 8" floppy doesn't require it at 4mhz or 6mhz. One thing that seems to be true, the longer the backplane the more likely it will ring and need termination. All Altairs seem to and IMSAIs seem to benefit if the cpu is z80 4mhz. The quietest unterminated or terminated backplane I own is an oddball 6 slot I have that is 4 layer technology with ground and power are on the middle two layers. I've found a few badly designed cpu cards and memory cards that were terrible in that they would introduce noise onto an otherwise quiet bus! Allison