Editing Atari Mega STE (section)

== Known issues ==

=== Cache instability at 16 MHz ===

The most commonly reported Mega STE issue is '''random crashing or instability when running at 16 MHz with cache enabled'''. This is typically caused by degraded cache SRAM chips (U3 and U4 on the motherboard) or failing cache control PAL ICs. Replacing U3 and U4 with known-good SRAM chips often resolves the issue.<ref name="exxoscache">{{cite web |url=https://www.exxosforum.co.uk/forum/viewtopic.php?t=3120&start=60 |title=MegaSTE Repair — Cache Issues |publisher=exxos Forum |access-date=2026-03-27}}</ref> Machines that crash at 16 MHz but run stably at 8 MHz should have these components investigated first.

=== Power supply capacitor degradation ===

The Phihong PSM-5341 PSU uses electrolytic capacitors that degrade with age. Symptoms include video noise, screen dimming during floppy access, random crashes, and eventual failure to power on. Recapping the PSU is strongly recommended as preventive maintenance. This PSU is shared with the Atari TT030.<ref name="exxospsu">{{cite web |url=https://www.exxosforum.co.uk/atari/last/psu/index.htm |title=Atari PSU Repair — The LaST Upgrade |publisher=exxos |access-date=2026-03-27}}</ref><ref name="exxosmste">{{cite web |url=https://www.exxosforum.co.uk/forum/viewtopic.php?t=300 |title=How to: Recapping the Mega STe Power Supply |publisher=exxos Forum |access-date=2026-03-27}}</ref>

=== Video ghosting ===

The STE and Mega STE suffer from a video ghosting artefact where bright objects on screen produce faint shadows or echoes. This is caused by impedance mismatches in the video output circuit and can be corrected with a simple resistor modification.<ref name="mandatory"/>

=== Software compatibility ===

While the Mega STE offers better compatibility with ST software than the TT030, some programs — particularly older games and demos — may fail when run at 16 MHz or with cache enabled. Using the GENERAL.CPX control panel to switch to 8 MHz with cache disabled typically resolves compatibility issues. Software that accesses hardware directly or uses cycle-counted timing loops is most likely to be affected.