Homebrew
In May 2005, it was discovered that PSPs using the 1.00 version of the firmware could execute unsigned code. PSPs could now run homebrew software, as there was no mechanism to check if the code had been digitally signed by Sony. A proof-of-concept "Hello World" was released to demonstrate this. This resulted in the release of a number of homebrew software, which were all built with the GNU GCC and GNU Binutils, modified to produce code for the PS2 and PSP (MIPS processor devices). In addition, it became possible to dump Universal Media Discs (UMDs) using a homebrew technique. These dumped UMD images can be written to a Memory Stick and executed, performing in exactly the same way as if they were being read from a UMD. While the version 1.00 firmware had been ripped (by de-soldering the firmware flash chip and reading it), there is currently no way to revert to this firmware from any version higher than 1.00. If you have 1.00 PSP, a homebrew program is available to save your 1.00 firmware, update your PSP to 1.5, and later downgrade again, using the saved firmware. and wish to update it to 1.5 while keeping the option to later revert to 1.00. The saved firmware is unique to each PSP, and so only PSPs of 1.00 can ever upgrade and return to 1.00.
Current Homebrew
On April 25, 2006, Sony released firmware version 2.70, which directly patched the exploit in the GTA savegame. As a result, there is curently no homebrew support for this version. With 2.7 came Macromedia Flash support, and hence a number of flash games have been created.
