Hi, sorry for the long update.
So I have tried using another board (Asrock 775i65PE) for booting the Installation Diskette using the same CPU, and it boots the disk, but it fails on loading the drivers on the next disk. I don't tinker with it because I don't use that board for my general usage.
I also tried using lower RAM (512MB) in this board and it still fails to boot the Installation Diskette.
Anyway, I'm still curious on why it fails to boot the Installation Diskette, is there any way to debug the process? Maybe if there's nothing can be done, I might try to install it using a Virtual Machine, and then clone it to the drive.
Installing OS/2 Warp 4.0 might be the last one to do if all above else fails haha