The hardware supports booting games from both the UMD and DVD drive, the DVD drive can even boot games from standard DVD-R/RW and so many prototype PSP games are actually written on standard rewritable DVDs.
In order to use the DevKit to play games you need a controller, and what better controller than the psp itself! A custom PSP
Controller Arm was provided with the devkit for such a purpose. It wasn’t a real psp and the inside board were very different to a retail psp, it was mainly just an interface for providing button in put and screen output for the developers to see what it would look like on a real psp.
Here is a tear down of the controler hardware by RetroGameTech 1:
When the PSP Go console came out there was an optional accessory for the development kit to switch the standard PSP controller to a version that is basically a PSP-Go shell with all the PSP chips ripped out and it is pretty much just used as a controller and display. 2
The testing tool tower contains both a DVD and UMD drive with a toggle to switch between the two, it contains a slot to insert the PSP memory stick, a usb-mini port, a headphone port and a port to connect the Commander Arm. It also contains a number of DIP switches but it is unclear what each DIP-switch does.
Notice that this does not have an ethernet port so can’t be used for debugging unless using the slow usb serial or WLAN interface 3
The front of the development Unit looks pretty much identical to the Testing tool (DTP-H1500), but on the back it contains an ethernet port to allow debugging with a host PC.
Since the development TOOL doesn’t have a hard drive and I can’t find any references to CDs that contains the development kit files, presumably developers had to logon to the SCE developer website to download the SDK, compilers etc for their PC.
A PSP SDK has never been leaked probably because it was just a download that most people would do and then throw away, much easier to loose than a physical CD like previous Sony SDKs.