Sorry I was referring to the AHT disks that ship with newer (intel) macs.
The terminology has changed over time and causes confusion.
Earlier, macs shipped with a hardware test cd that was os 9 running techtool. Later apple started writing some of their own test code, but called it a hardware test disk. these were primarily provided to service providers though not to users. These were produced for all powerpcs through G5. These ran in openfirmware.
When the intels came out apple shifted gears and produced a dedicated Apple Hardware Test (AHT) for each model and shipped that with the computer, and produced a less specific Apple Service Diagnostic (ASD) for the service providers. A typical ASD supports maybe 10 different models. All AHT support ONE model. ASD and AHT for intel all boot in EFI except for the recent OS testing variations.
Any straight numbered (2.3.3, 2.5.8, 2.6.3) is an old AHT and supports multiple models. Any 3aXXX is an AHT and supports one model. Any 3sXXX is an ASD and supports multiple models.
I believe apple now allows download of all AHT, even the current models. Apple does not allow download of ASD without a GSX account. A typical AHT image is 50mb. The latest ASD come on multigigabyte segmented disk images and include both a bootable EFI image and a bootable OS tester. The OS tester is sufficiently large to require installation on a hard drive partition. I don't usually use the OS tester because I get what I need from simply having a bootable 10.5 installation to try.
