Editing Atari Mega STE (section)

=== Memory ===

The Mega STE uses '''30-pin SIMM''' (Single Inline Memory Module) slots for RAM, a significant improvement over the soldered DRAM of the Mega ST. Four SIMM slots accept 256 KB or 1 MB SIMMs in matched pairs, providing configurations of 1 MB, 2 MB, or 4 MB.

{| class="wikitable"
|-
! Configuration !! SIMMs required
|-
| 1 MB || 4 &times; 256 KB
|-
| 2 MB || 2 &times; 1 MB (+ 2 empty slots, or 2 &times; 256 KB in remaining slots)
|-
| 4 MB || 4 &times; 1 MB
|}

'''Parity SIMMs should not be used.''' Multiple documented cases have shown that parity SIMMs cause instability, particularly under load or when the power supply is degraded. If parity SIMMs are installed, the parity chip should be removed from each module.<ref name="mandatory">{{cite web |url=https://www.exxosforum.co.uk/forum/viewtopic.php?t=1585 |title=Mandatory Fixes |publisher=exxos Forum |access-date=2026-03-27}}</ref>

Memory access is managed by the GST MCU (GLUE-Shifter-MMU combined chip), which handles address decoding, DRAM refresh, and bus arbitration with the CPU, BLiTTER, and DMA controller.