Updated: 06/30/2020 by Computer Hope

In computing a multiplier, CPU multiplier, clock ratio, clock multiplier, CPU Core Ratio is the speed ratio between the CPU (central processing unit) and the FSB (front-side bus). For example, a CPU with a multiplier of 20 and an external clock of 133 MHz has a CPU speed of 2.66 GHz.

Not all computer motherboards have the option to adjust this through BIOS. However, for those that do, you can change the computer multiplier by entering BIOS setup and looking under the CPU or overclocking section. When changing this setting, it's important you realize the potential issues that arise when overclocking a computer as mentioned in our overclock definition. Below is an example of what this may look like in your BIOS setup.

CPU multiplier CMOS setup setting


Some motherboard manufacturers for safety reasons only allow this value to be increased so far. If you cannot increase the value, it's likely you're at the maximum.

BUS, CPU terms