Diagnostic system

An apparatus for testing computer systems comprising:

• a. a base unit, the base unit comprising a central processing unit for executing instructions, issuing commands, and receiving data from a first computer system;
• b. a first connecting module which contains at least one connector for coupling to the first computer system, said connector being coupled to an existing connector on the first computer system, said first connecting module being interchangeable with a second module for interfacing with a second computer system, said at least one connector comprising a disk drive connector;
• and
• c. a first nonvolatile memory module coupled to the base unit, the first nonvolatile memory module comprising a first set of tests for the first computer system, the first nonvolatile memory module being interchangeable with a second nonvolatile memory module comprising a second set of tests for a second computer system, said first set of tests including an initialization circuit causing said first computer system to initially attempt to execute an internally-stored set of diagnostic routines, and if said initialization circuit is unsuccessful at causing said first computer system to attempt to execute said internally-stored set of diagnostic routines, then said initialization circuit causing said apparatus to emulate a disk drive through said disk drive connector and causing said first computer system to perform a bootstrap initialization of said first computer system from said apparatus by loading a set of externally-stored diagnostic routines from said first nonvolatile memory module.