To avoid misunderstanding, as I understand from mainframe talks, many of them was customizable like modern FPGA machines, as they even considered make custom ha

To avoid misunderstanding, as I understand from mainframe talks, many of them was customizable like modern FPGA machines, as they even considered make custom hardware (imagine, you could order fully custom machine with additional registers, custom ALU, etc), that's why I compare custom microcode of CISC to FPGA, and why I think it is lost feature, just not existing in mini's and in micro's.