What software is needed to make a psx game

[LeeSim]

OK, the other guys need to ACTUALLY READ A POST before submitting an answer!!!
What you want to know is how to program a Playstation game of your own from scratch right??
Well I don't know if any programs are available, but a while back Sony released a BLACK Playstation call a NET YAROZE for home programmers to write their own games ... maybe for publication. These were programmed in C++ as far as I can remember & came with some discs with libraries containing routines for standard functions (Joypad control et.c.) which could be edited to your own parameters.
This was all backed up by a website:
www.scea.sony.com/net/index.html US site
www.scee.sony.co.uk/yarinfo/index.html UK Site
www.scei.co.jp/net/ Jap Site
www.geocities.com/TimesSquare/Alley/2200/ Webzine
http://dir.yahoo.com/Recreation/Games/Video_Games/Systems/PlayStation/Net_Yaroze/ Yahoo page with some info
This was quite a while ago though & since then Sony stopped making the Yaroze.

I know this may not help you much, but if other people READ this reply & understand what you want, then maybe they can give you the info you need.

Let me know how you get on...

Good Luck!