What happens to the memory speed when installing PC-4000 modules alongside PC-2400 modules?

When installing memory modules of different speeds, the system typically defaults to the speed of the slowest module in the configuration. In this case, if PC-4000 modules (which operate at a maximum speed that corresponds to a 500 MHz effective clock rate or 4000 MT/s) are paired with PC-2400 modules (which operate at a maximum speed that corresponds to 300 MHz effective clock rate or 2400 MT/s), the entire memory subsystem will operate at the speed of the slower PC-2400 modules.

Thus, all memory in this setup will function at the speed of the PC-2400 modules, which is 300 MHz effective speed, thereby ensuring system stability and compatibility. This is standard behavior across most motherboard and memory controller architectures, ensuring that the faster memory does not attempt to operate at a higher speed than the slower memory can handle.