Final answer:
In the Intel X58 (Nehalem) chipset, the 64-bit Front Side Bus (FSB) was replaced with the QuickPath Interconnect (QPI), which provides higher bandwidth and lower latency for better performance and the ability to scale multi-processor systems.
Step-by-step explanation:
The 64-bit Front Side Bus (FSB) was replaced with the QuickPath Interconnect (QPI) in the Intel X58 (Nehalem) chipset. QPI is a high-speed, point-to-point interconnect bus between the processor and the chipset. This replaced the older FSB architecture for several reasons, including the provision of higher bandwidth and lower latency, which are essential for improved system performance and efficiency. Moreover, QPI allowed for easier scaling of multi-processor systems which is an advantage in high-end computing. The Nehalem architecture's move to QPI was part of a broader shift in CPU architecture that aimed towards better optimization for multi-core processors.