PlayStation Development Network

Perhaps not news to many, but this was something I wondered for 30 years, if the PS1 BIOS even supported the mouse at all since the cursor resembled a mouse cursor. After finally obtaining a PS1 mouse, it DOES support the mouse! But not only that, the cursor changes into a crosshair.
I somehow both expected the mouse to work, and possibly not, but I most certainly didn't expect that the cursor also changes its shape as well.

I tried in emulators to no avail, but when I got the PS1 mouse, I learned it is supposed to be in port 1 per the box, whereas when I tried this on emulators I only ever put the mouse virtually on port 2, not knowing it wasn't supposed to be in that port for the BIOS interface.

That is actually very interesting. I never would have thought that would be a thing.

I always thought it was a bummer that WarCraft II on Playstation doesn't actually support the mouse. It seems a fair number of titles do support it. And it seems there are some projects to make USB Mice/Keyboard to PS1 adapters. I may have to keep in mind that the Mouse exists for homebrew projects.

It's really cool to know that the PS1 BIOS not only supports the mouse but also changes the cursor to a crosshair, this opens up a lot of new potential for homebrew projects and improves the user experience on the classic console!

It has been known for a long time that the BIOS supported the mouse. It's just that a lot of PlayStation 1 gamers didn't use the mouse so it was a hidden feature. It's somewhat like the file allocation table undelete command for Memory Cards in the BIOS, albeit that one is truly hidden but if I recall it was documented in a game manual which is how it was found (and it was also found by reverse engineering the BIOS).