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System powered on when plugging in PS/2 keyboard

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First post, by Kahenraz

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I thought it was rather odd that my system (a 440LX) turned itself on when I inserted a PS/2 keyboard while the system was off but plugged in. The lights on the keyboard also come on whenever it is disconnected and reconnected. I know that these keyboards should never be hot plugged while the system is turned on, but this makes me nervous. I tried to replicate the issue but couldn't.

Is it normal for the keyboard lights supposed to come on momentarily when plugging on a PS/2 keyboard on a powered down system?

There is an option in the motherboard BIOS to "Power Up By Keyboard", but this option is disabled.

Reply 1 of 2, by BitWrangler

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Sometimes there's also a "KB_PWR" or something jumper on the board which enables keyboard powerup... ... ... in some instances that then disables the case power button for wake-up and you think your board is dead until you hammer the space bar.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 2 of 2, by rasz_pl

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afaik every keyboard will blink once when receiving power for the first time - this signals keyboard microcontroller starting up. Then during normal PC power up sequence you get the second blink when bios initializes Keyboard controller and sends Reset command to the Keyboard.
https://wiki.osdev.org/%228042%22_PS/2_Controller https://github.com/qb40/keyboard-controller

https://github.com/raszpl/FIC-486-GAC-2-Cache-Module for AT&T Globalyst
https://github.com/raszpl/386RC-16 memory board
https://github.com/raszpl/440BX Reference Design adapted to Kicad
https://github.com/raszpl/Zenith_ZBIOS MFM-300 Monitor

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