Editing Sinclair QL Troubleshooting Guide (section)

=== The IPC and the Hermes replacement ===

The Intel 8049 IPC (IC24) handles the keyboard, sound and serial input, and talks to the rest of the machine through the ZX8302. Original IPCs carry custom Sinclair firmware and are not a stock part, so a failed one cannot simply be bought.

The community answer is '''Hermes''', a drop-in modern replacement for the IPC. As well as replacing a dead device it fixes several long-standing QL shortcomings, and it is the standard recommendation when an IPC is suspected.<ref name="qlf-diag">[https://theqlforum.com/viewtopic.php?p=57915 "Sinclair QL Diagnostic"], The Sinclair QL Forum. Community discussion of IPC/ZX8302 fault isolation and the Hermes and replacement-8302 options.</ref>

Because the IPC sits behind the ZX8302, a fault in either can look like the other. If keyboard, sound and serial input are '''all''' dead while the machine otherwise runs, suspect the IPC or its link to the ZX8302 rather than the keyboard.<ref name="qlf-diag" />