Amiga 2000: ATX PSU vs. TICK signal

[vk3heg]

LoadWB wrote:
While browsing the A2000 Schematics I noticed J300, which selects between the TICK signal from the power supply and (the schematics are in another room, so I'm relying on recall here)  the VBLANK signal.

Would it be such an issue to use the VBLANK signal in lieu of the missing TICK signal from an ATX power supply?  Wouldn't that only make a difference with the internal clock when the system is in a video signal mode opposite of its native mode (PAL->NTSC, NTSC->PAL)?

I use this method for my A3000. I have a 300w AT power supply, providing power and had to use this jumper on the motherboard.  The ami, works great and as it should (I don't do video work though, and use a cybervision rtg graphics card for non amiga modes).