Comparison of IntSim's Results with Actual Data of a Commercial Microprocessor
In this section, IntSim is used to predict wiring requirements of a commercially available 65nm 3GHz high-performance dual core microprocessor . The predictions for number of interconnect levels, wire pitches and logic core power are compared with actual values of these quantities. Details of this chip’s transistor parameters and number of gates in each core are obtained from published data in . The dielectric constant for interconnects is 2.9, contacted gate pitch is 220nm and supply voltage is 1.325V . Rent’s constants k and p are chosen as 4 and 0.55 respectively based on guidelines in  that custom chips would have Rent’s parameters around these values. Area of a logic core is obtained from die photos and published information about total die area . Package technology parameters are obtained from data on older high-performance chips with the assumption that package technology does not scale. The values of wire pitch obtained are not very sensitive to package technology parameters, so these rough calculations are not expected to cause significant error.
The above table shows a comparison between wire pitches predicted by IntSim and actual wire pitches used for that technology . IntSim predicts the number of metal levels to be 8, which is exactly what is used for that interconnect technology. The wire pitches predicted by IntSim are similar to the ones actually used. One notable difference is that IntSim chooses wire pitches of two adjacent orthogonal metal levels to be the same, while the actual data has different wire pitches for adjacent orthogonal wiring levels.
IntSim also predicts the total power of logic cores of this chip to be 62.3W, while total chip power based on measured data is 80W . Published data is not available regarding the percentage of chip power consumed by caches and I/Os for this microprocessor. However, another 65nm processor had 19% of its total power consumed by these components and 81% of total power taken up by logic cores . Assuming the processor analyzed with IntSim has similar numbers, the logic core power for this processor is 65.6W, which is quite close to IntSim’s prediction of 62.3W.