How to Calculate the Speed of an Intel QPI?
The QuickPath Interconnect (QPI) communications architecture was developed as a replacement for the traditional motherboard Front Side Bus (FSB). Both FSB and QPI are designed to quickly move data from different locations on the motherboard, such as from the CPU to the main memory. The total QPI throughput speed is obtained by calculating different specifications of the signal, then multiplying them by the base frequency. This includes the data rate, the QPI link width and the data width.
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Instructions
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Determine the base frequency. QPI-capable processors use a 2.4, 2.93 or 3.2 GHz frequency, as of 2011. The base frequency is determined by dividing the processor's GT/s rating by two. The GT/s rating is listed in the processor's specifications.
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Multiply the base frequency by the number of bits transmitted per clock cycle. For example, QPI-capable processors transmit two bits per clock cycle, one on the rising edge and one on the falling edge, as of 2011.
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Multiply the previous result by the width of the QPI bus, which is usually 20.
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Divide the data bits of the payload by the flit bits. The data payload is typically 64 bits. The flit includes the data payload with eight bits reserved for error detection and eight bits for a header. Using this example, the result is eight tenths (64/80). Multiply this number by the previous result.
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Multiply the previous result by the number of links in the QPI.
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Divide the previous result by eight to obtain the QPI throughput speed in gigabytes per second.
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