Why are there several balls missing from the underside of the Pentium III – Low Power processor?
The balls that are depopulated are one or more of the VID signals. In a design, the VID[4:0] signals from the processor should be connected to the voltage regulator device. These signals tell the voltage regulator what core voltage to produce for the processor (based on a mobile VID voltage table – see Pentium III processor – Low Power datasheet). The VID signals should have external pull-ups on the motherboard (some voltage regulator devices already have internal pull-ups on these signals). A populated VID ball on the processor is connected to GND internally. The voltage regulator device will interpret this as a ‘0’. If a VID ball is not populated, the pull-up on this signal will cause the voltage regulator to see a ‘1’. Through this method, the proper VID code is presented to the voltage regulator, which in turn will provide a processor specific core voltage.
Related Questions
- What are the layout recommendations for the Intel Pentium III- Low Power (and Celeron Processor - Low Power) GTL+ PSB (Processor Side Bus)?
- What is involved in migrating from the Intel® Pentium® II - Low Power processor to the Pentium III - Low Power processor?
- Why are there several balls missing from the underside of the Pentium III - Low Power processor?
