Editing Diagnostic Serial Console (section)

== Important Notes ==
* Not all diagnostic tests work on every model; compatibility varies with ROM version.
* SE/30 and other 256k ROM Macs do '''not''' support certain diagnostic commands listed here.
* There is '''NO''' overflow protection when testing memory. If you attempt to address memory space beyond what is installed, the system will write to and read from wrapped memory locations, typically the first byte of memory. This is normal opperation and actually how the system calculates the RAM capacity.
** If you are testing with any 1MB installed, the memory won't overflow. This can be an issue if you're testing RAM manually.
* if you enter diag mode via NMI button, the Identify (''5) will report 000001300F, so won't tell you RAM size, but if you ask for RAM size'' ''(''T000000010001) then it works and subsequent Indentify (*5) calls work again.
* Algorithmic memory tests (T0002, T0005, T0006) are hardcoded to test 8MB address space and will fail on systems with less memory installed. This represents normal diagnostic behavior, not hardware failure.
* The diagnostic interface operates independently of Mac OS memory management and can access hardware directly, enabling component-level troubleshooting impossible through normal software methods.
* Modern reproduction boards such as the [[Macintosh SE/30 Reloaded Logic Board|SE/30 Reloaded]] may exhibit identical diagnostic behavior to original Apple hardware, confirming that diagnostic failures often represent normal responses to hardware limitations rather than board-specific issues.
* The "[[Sad Mac Error Codes|Simasimac]]" pattern (vertical stripes at startup) is a common SE/30 issue often caused by leaking capacitors on the logic board causing circuit corrosion.