 The "field value" actually controls that part of the CPU.With this type of microcode, a designer explicitly chooses to make a slower CPU to save money by reducing the unused bits in the control store; however, the reduced complexity may increase the CPU's clock frequency, which lessens the effect of an increased number of cycles per instruction.As transistors became cheaper, horizontal microcode came to dominate the design of CPUs using microcode, with vertical microcode being used less often.