IBM eServer xSeries 300 User Reference Manual page 74

One long and one short beep
One long and two short beeps
One long and three short beeps
Two long and two short beeps
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xSeries 300: User's Reference
Note: If you just connected a new mouse or other pointing device, turn off
the server and disconnect that device. Wait at least 5 seconds; then,
turn on the server. If the error message goes away, replace the device.
POST encountered an error on a video adapter. If you are using the
integrated video controller, call for service. If you are using an optional video
adapter, replace the failing video adapter.
A video I/O adapter ROM is not readable, or the video subsystem is defective.
If you hear this beep combination twice, both the system board and an
optional video adapter have failed the test. This beep combination might also
indicate that the system board contains a failing component.
The system-board video subsystem has not detected a monitor connection to
the server. Ensure that the monitor is connected to the server. If the problem
persists, replace the monitor.
POST does not support the optional video adapter. This beep combination
occurs when you install a video adapter that is incompatible with your server.
Replace the optional video adapter with one that the server supports or use
the integrated video controller.