Hmm from pcsx2's change log:
[ Legend: ]
[ + Added feature ]
[ * Improved/changed feature ]
[ - Bug fixed (we hope) ]
[ ! Attention (Notes) ]
* 21/05/05:[-] More PS1 compat fixes
[!] Seems the GPU->GS is done by the PS1DRV, gotta find out more
(linuzappz)
* 19/05/05:[+] PS1 games kinda boot now as well
(linuzappz)
so , it seems that pcsx2 will "run" ps1 games
.. This isn’t strange... Since the whole ps1 compatibility is done by a part of ps2’s bios (ps1drv) so, if bios is correctly emulated, and iop is correctly emulated too, ps1 games should work 
I hope this does not violate the rules... (From the cvs change log)
[ Legend: ]
[ + Added feature ]
[ * Improved/changed feature ]
[ - Bug fixed (we hope) ]
[ ! Attention (Notes) ]
* 21/05/05:[-] More PS1 compat fixes
[!] Seems the GPU->GS is done by the PS1DRV, gotta find out more
(linuzappz)
* 19/05/05:[+] PS1 games kinda boot now as well
(linuzappz)
so , it seems that pcsx2 will "run" ps1 games
I hope this does not violate the rules... (From the cvs change log)