The maximum resolution for external monitors on an Eos Classic console depends on the type of connection.
Eos can send external monitors using VGA a maximum resolution of 2048x1536.
Eos can send external monitors using DVI a maximum resolution of 1600x1200.
Setting a monitor above this resolution can and will cause graphic anomalies and reduced performance. There have been two different video cards used in Eos production; these both share the same limitations.