Every motherboard is different I suppose. On my motherboard, I don't have to unplug the PSU to reset the CMOS. Also, I don't have to press the power button.
However, I recently experimented with a broken graphics card. Booting with it caused my BIOS to hang, even when using another graphics card afterwards. Resetting the BIOS only worked with my old card AND a PCI card inserted. I also had to press the power button to get it to reset properly.
But if I overclock too much, moving the jumper for 2 seconds will work.
TheMajorMMX - Intel P200 MMX @ 225Mhz - V-Tech (PcPartner) Baby-AT mb w/ Intel Triton TX chipset - Nvidia Riva TNT2 M64 w/ 16MB - 256MB M-Tec SDRAM - Still running.....