IBM was ferrite happy for a while towards the end of the big water cooled mainframe era. Our power supplies were basically becoming 36kw radio stations. We used to get ferrites in the 100 piece bag with 200 ferrite "halfs" and 100 plastic clam shells. We were clipping them on everything. We had another round of this with wire printers. I still have a big bag of those smaller ferrites if anyone wants some. (the size on a printer cable)
