<Take that 800 mA pulse, and multiply it by the length of all the wires <hooked to each drive line. What you end up with is a rather good radiator <of high-frequency hash! Many machines housed the entire core assembly, <including drivers, in a different box than the CPU for this reason. <PDP-8/E's and -8/F's, where the memory does sit in the CPU box, have a <special shielding card that segregates the memory from the rest of cards <to keep this hash out of the CPU circuitry. also to keep out of local TVs. Some of the core systems were boxed to keep a constant temperature as ferrites are temerature sensitive. Allison