No. This is the width of the FSB (Socket A) or HTT-Link (Socket 754 & 939); this can also mean the width of the memory bus. Think of 'bus width' as a highway. For a lack of a better example, a 64-bit wide bus is 4 lanes; a 128-bit bus is 8 lanes. Theoretically, the more lanes there are, the more data that can be passed through.
For your processor to be 64-bit, assuming you're using a Sempron, it must be Socket 754 and have been purchased recently (since they were released about a month or two ago).
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