The lower yields than TSMC would also cause lower profits when making chips for external customers, so Intel must really improve their yields.
Old Intel fabs are refurbished, by installing modern equipment, so they are converted from old CMOS fabrication processes to recent processes.
Before being converted, the fabs spend a few years making peripheral chips that complement the Intel CPUs, e.g. the so-called south-bridge, which may be packaged together with the CPU for laptops or it may be a separate IC package for desktops, and which does not need a fabrication process as dense as the CPUs.
Old Intel fabs are refurbished, by installing modern equipment, so they are converted from old CMOS fabrication processes to recent processes.
Before being converted, the fabs spend a few years making peripheral chips that complement the Intel CPUs, e.g. the so-called south-bridge, which may be packaged together with the CPU for laptops or it may be a separate IC package for desktops, and which does not need a fabrication process as dense as the CPUs.