Item description:

The PlayStation driver video mode negater (PS1VModeNeg) is a tool
that selects the correct video mode for your imported PlayStation game,
regardless of what your PlayStation 2 console's PlayStation driver (PS1DRV)
has been fixed to use.

Depending on the boot ROM (aka "BIOS") of the console, one of these two different methods will be used:
Patch the video parameters initialization function.
Patch the ROMVER string parsing function (Fools the driver to thinking that your console is from another region).

#1 is used for consoles belonging to the SCPH-70000 (ROM v2.00) series and newer.

The PlayStation drivers of the SCPH-75000 appear to have been coded to be universal, like with the rest of the design of the slimline consoles in general. This means that full compatibility with import games should be achievable with minimal patching.

Older drivers are more difficult to tackle, as they have been hard-coded to work with games from your console's region. e.g. NTSC consoles appear to have a built-in compatibility list and assumes that your games will use the NTSC video mode. Code for supporting the video mode from the other region (e.g. NTSC games, for a PAL console) will have to be added.
It's probably also not too surprising if some games work well on only consoles native to the region that they are from, due to the region-specific game compatibility list.

On older consoles (SCPH-70000 and older), please take note that there is a risk that your TV might blow up or gets damaged, if my code turns out to be faulty. That hasn't happened to the two TVs I've tested on, but I don't want to guarantee anything because the method I use involves tweaking with the values that the PS1 driver appears to write to the GS's SYNCHV register (One of the undocumented registers that Sony had prohibited external developers from writing to directly).