DVO7
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← Repair Guides|Memory Upgrade 512 KB → 1 MB (EII+ spec)
hard150 min

Memory Upgrade 512 KB → 1 MB (EII+ spec)

Symptoms this guide addresses

  • •Want longer sampling time
  • •Want EII+ capability on a base EII

Tools required

  • •Soldering iron
  • •Desoldering tool
  • •32× 41256 DRAM
  • •CD74HCT138E ×2
  • •EII+ OS ROM

Overview

A base Emulator II (512 KB) can be brought up to the EII+ 1 MB spec. The extra memory is organised as two switchable 512 KB banks — a single sample cannot span both banks.

Procedure (summary — see the service manual for exact placement)

  1. Remove the piggyback memory board.
  2. Replace the 32× 4164 DRAMs with 32× 41256 DRAMs.
  3. Change jumpers: remove W2/W3, add W3→W4 and W1→W2.
  4. Replace decoder ICs IC11 and IC98 with CD74HCT138E.
  5. Flash/fit the EII+ OS ROM.
  6. Rev 0 digital boards also require cutting specific PCB traces; Rev 1 boards need only the wiring changes above. Identify your board revision first.

Source: eiiiforum memory-upgrade thread. This is an advanced mod — work from the service-manual schematics and double-check board revision before cutting anything.

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