keyboard error or no keyboard present

Pentium MMX200 G586SPA motherboard Sis 5511 chipset, Award bios Modular V4.51PG, Win 95.

This set was working OK. I tried to insert a PCI modem. It started the BIOS error of “keyboard error or no keyboard present. I removed the modem but same message. I tried different keyboards both AT and PCI type. There are voltages at the keyboard pins as follows: Pin1=4.2V, Pin 4=5.8V, Pin5=4.2V, however, when the power is switched on the keyboard light does not flash or lights.

Keyboard is dead and I can not set up bios, firmware or any other thing. What can I do apart from assuming it is the motherboard fault and throw it away.