The L3 cache helps improve the overall performance by reducing latency and speeding up data access between the CPU cores and the main memory. L3 intel core i7-9700 @ 3.00ghz Cache is a larger, slower cache compared to L1 and L2 but plays a crucial role in reducing bottlenecks during data access. It is shared across all cores of a multi-core processor, which helps in improving communication between them. The L3 cache acts as a buffer, storing frequently used data and instructions for quicker access by the CPU.