Dual NTSC/PAL imports need swap trick to boot

[ravichanker]

I bought back a few dozen ps1 games from Bangkok to Australia
The sales girl said they are PAL/NTSC - "work on both" despite having only NTSC written on the cover
My PAL PS1 is modchipped and plays PAL backups no problem
However I can only get these "NTSC/PAL" games to boot using the swap trick
(that is boot the player on another PAL disc and swap it)
The games then run ok and in full colour so, from my readings, I guess the games indeed do have a PAL capability or they could only run in black and white
A forum posting on anothr site said there is a BIOS in some PAL PS1 picking up the NTSC (& visa versa) preventing boot up using foreign discs
So if there is already some kind of NTSC/PAL patch on these games would an ordinary NTSC- PAL patch achieve anything anyway. That is would an NTSC - PAL patch remove the NTSC data from these games ?
Does the answer lie in a chip or in alteration of the image file or perhaps something else?
The patches I attempted did not result in working copies and I tossed them, thinking they were coasters before I stumbled apon the swap trick, but I can now only supect they would have worked using the swap trick. So it seems a patch may not be the answer
Can anyone offer a definitive diagnosis and solution
If possible I would prefer not to have to do this swap trick or buggarise with patches.
Ravi