Sounds like you need a new keyboard.

And try plugging your mouse into your Pentium laptop to see what happens.

I had the impression that those "two to one" connectors required the laptop to explicitly support them.

@keenmaster486
Keyboard works well on it's USB-PS/2 converter with Pentium laptop, mouse works as well. Converter in 486 doesn't, except one port and only mouse, not keyboard.
@Jorpho
I started to think the same way, they probably just do not support it. But should keyboard work there or it is just PS/2 mouse port were back then?

What does the label on the port say?

No label on any ports there
http://h20565.www2.hp.com/hpsc/doc/public/dis … mr_na-c01125641
This manual says it is both for keys and mouse, but... problem is keyboard doesn't work, maybe because it connected to PS/2 - USB converter? But converter works in Pentium I laptop

1Keyboard/Mouse Connector
2The keyboard/mouse connector can be connected to a PS/2 mouse or an external
3enhanced keyboard. Connecting the mouse/keyboard connector to a mouse
4disables the integrated trackball, while connecting the mouse/keyboard
5connector to an external keyboard disables the internal keyboard.

It is meant to connect either a keyboard or a mouse directly. An Y-cable won't work. You may have to reboot / repower after you plugged / unplugged a device as it needs to detect what type of device is connected.

If that doesn't help it is likely a compatibility problem, since the mouse works and keyboard/mouse use the same data pins.

Since every PS/2 port has 2 unused pins and the devices only use two communication lines I've always wondered if those 'combination ports' found on motherboards & laptops would allow both a keyboard and a mouse simultaneously by providing the data/clock lines for the additional device on the unused pins so that you'd only need a Y-cable that would route the pins correctly, but I've never got around to test that.

The problem is I don't have ps/2 keyboard to test, I'll try to get it from someone just for try

133MHz wrote:

Since every PS/2 port has 2 unused pins and the devices only use two communication lines I've always wondered if those 'combination ports' found on motherboards & laptops would allow both a keyboard and a mouse simultaneously by providing the data/clock lines for the additional device on the unused pins so that you'd only need a Y-cable that would route the pins correctly, but I've never got around to test that.

The wikipedia article on PS/2 ports actually mentions that the two unused pins are some times used for mouse input using splitter cables:
https://en.wikipedia.org/wiki/PS/2_port

(Pin-out image on the right)

Good to know. 😀

Well. I got another ps/2 keyboard. works on that laptop. So now both mouse and keyboard works there, but not together with that splitter 🙁
anything works if you plug it in keyboard port on that splitter, nothing works on mouse port. When I plug keyboard just to mouse one on splitter it says Keyboard error. internal keyboard is still working