Much has been made of the need to use ultra low ESR caps for the CPU power source.
These caps have specified impedance at 100Khz that will be effective for power supply ripple. However what about the frequency spectrum above 100Khz that goes way up to a number Ghz. A processor operating with 400FSB and 2Ghz will generate wide band noise on the power rails. Normal digital circuit design requires that ceramic capacitors are placed as close as possible to the supply pins of each chip so that these frequencies can be bypassed. Electrolytic caps present themselves as a high impedance at these ultra high frequencies. I cannot see the use of ultra high frequency capacitors around the the CPU. Perhaps they are very small or laminated planes in the motherboard are used to remove these frequencies.
Does anybody have a reference that indicates how complete filtering is achieved? I have tried Google searches.
These caps have specified impedance at 100Khz that will be effective for power supply ripple. However what about the frequency spectrum above 100Khz that goes way up to a number Ghz. A processor operating with 400FSB and 2Ghz will generate wide band noise on the power rails. Normal digital circuit design requires that ceramic capacitors are placed as close as possible to the supply pins of each chip so that these frequencies can be bypassed. Electrolytic caps present themselves as a high impedance at these ultra high frequencies. I cannot see the use of ultra high frequency capacitors around the the CPU. Perhaps they are very small or laminated planes in the motherboard are used to remove these frequencies.
Does anybody have a reference that indicates how complete filtering is achieved? I have tried Google searches.
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