The nomenclature ARM (the company) and its licensees use to identify processors can seem confusing because of the wide spectrum of vendors who sell ARB-based integrated circuits. You'll find a list of 200+ licensees for the Cortex, ARM11, ARM9, and ARM7 processor families on the ARM Web site. With four processor families, identification of devices shouldn't cause problems. But, within those families, you have subgroups:

And this list doesn't include early ARM devices or predecessors to the families above. So, following the ARM families can get difficult.

To help developers, Dick Selwood at the Embedded Technology Journal wrote, "Unpicking the Codes: A Guide to ARM Architecture and Processors." You will find the complete article here.

Also, just because a chip vendor includes an ARM core in a device, it doesn't mean they have provided all of the features developers might need. As Selwood puts it, "What debugging elements have they incorporated in the hardware? How many pins are dedicated to Trace? How many hardware breakpoints are built-in? Is it worth saving a few cents per device if a bug is going to be difficult to eliminate and could cause you to miss the sweet spot in the market?"

So, look beyond the ARM- and vendor-specific nomenclature confusion and concentrate on how you want to solve a problem, the tools you'll use and the capabilities of the ARM device your vendor-of-choice provides. After all, ARM licenses intellectual property and does not make chips. Thus, the chip vendors alone determine how they'll implement the ARM code--and what they'll leave out. Keep your eyes on capabilities rather than try to decrypt the various ARM product codes.
--Jon Titus