Multi Firmware Module
Multi Firmware Module was announced on April 24 2006 . Multi Firmware Module contained a different PSP firmware to the one onboard the PSP itself and can be booted from, or copied to, the PSP's original NAND flash chip, unbricking the PSP. It was planned for release upon the acquisition of a suitable manufacturer, but it seems like it will never be released.
The PSP modchip ("Undiluted Platinum") was announced on May 28 2006. It allows the user to run two separate firmwares, one on the PSP itself, and one on the modchip. It also allows the restoration of corrupted firmware ("unbricking"), and so may lead to the creation of custom firmwares, allowing the full range of homebrew, while still being able to play the latest games. However, this chip may not run on all PSP hardware, due to the lower voltage of newer, TA-082, PSP boards.
Undiluted Platinum was released on June 26 2006. However its installation required some very careful soldering, and many users did not wish to install this modchip. On July 23 2006 the custom firmware Epsilon Bios was released, it required the Undiluted Platinum to be used.
The day after Undiluted Platinum's release, a kernel exploit for 2.50 and 2.60 was revealed, aggravating many users who purchased the modchip just to downgrade from those versions.
A new modchip called "PSP-Devolution" is in development state. It seems that it has similar features from the Undiluted Platinum chip, and it will be compatible with all motherboards (TA-079 to TA-086), also providing TA-082 recovery.
According to PSP-Devolution.com, sales of the PSP-Devolution modchip should have commenced on April 16 2007 .
A (TA-079 to TA-081) version is now available which runs on 3.3V and on June 6 2007 a version for TA-082+ motherboards was made available which runs on 1.8V. Info at mod-chip.com
PSP modchips have been made obsolete with the creation of Pandora's battery. Many modchip adopters bought their chips to unbrick or downgrade, both functions now available free.