2MB RAM Amiga 500/500+

2MB-board set.jpg2MB memory upgrade for Commodore Amiga 500/500+

Introduction

This is a two megabyte memory upgrade for the Commodore Amiga models 500 and 500+. It is a modern replacement for the original A501 0.5MB (512K) upgrade from Commodore.

Add up to 2MB of memory to the machine depending on motherboard revision and Kickstart version (see below for details). Can provide both chip RAM and slow RAM in one expansion.

On the Amiga chip RAM is used for graphics and sound. Many games were written to use additional chip RAM to provide better graphics, sounds, music, higher resolution TV images and reduced disk swapping. Slow RAM can be used by workbench and many games also support this memory.

The upgrade can be fitted with a realtime clock chip (RTC) and clock backup battery (CR2032). 

Upgrade Description

The upgrade consists of a memory board and an optional Gary adapter.

The memory board has the 2MB memory chip, logic, A500/A500+ jumper and RTC socket. The RTC socket allows an RTC chip to be fitted to an Amiga 500 if the user wishes. Amiga 500+ computers have an RTC chip fitted from the factory. The memory board fits in the "trapdoor" under the keyboard.

Installed without the Gary adapter, the memory board will act as a Commodore A501+ memory upgrade providing 0.5MB on an Amiga 500 and 1MB on an Amiga 500+.

The optional Gary adapter brings extra signals to the memory board. This allows more of the memory on the board to be used by the Amiga - more than the original Commodore upgrades. The Gary adapter must be fitted to access the full 2MB on your Amiga.

The memory board has an additional connector for optional jumper wires to the Amiga motherboard. These wires are required to get chip RAM and slow RAM at the same time. The wires must be soldered to the Amiga so only attempt this if you have the correct tools and are confident in soldering your Amiga.

System Requirements

The upgrade has been tested on Amiga 500 revision 3, 5 and 6A as well as Amiga 500+ computers.

How much memory is available for use depends on Kickstart ROM version, motherboard revision and Agnus (OCS/ECS) version.

Amiga 500

The upgrade will work in any Amiga 500. However not all 2MB is accessible on the older machines.

Kickstart v1.3 (or greater) is required to use the Gary adapter. Older versions of Kickstart do not boot with more than 0.5MB of extra RAM. The Kickstart ROM can be upgraded on all Amiga machines. Revision 3 and revision 5 computers shiped with Kickstart v1.2. For more information see Kickstart Wikipedia.

An ECS Agnus (8372 or 8375) is required for 1MB chip RAM. The original OCS Agnus (8370 or 8371) found in revision 3 and 5 machines can only access 0.5MB. For more information see Agnus Wikipedia. Revision 5 A500s can be upgraded to a 1MB Agnus - search the forums for details.

A jumper wire soldered to JP2 and the Gary adapter are required for the full 2MB to be accessible.

Amiga 500+

The upgrade will work in any Amiga 500+.

Jumper wires and the Gary adapter are required for the full 2MB to be accessible.

Configurations

Kickstart version 1.3 or greater is required to use the Gary adapter.

A 1MB (ECS) Agnus is required for 1MB chip RAM on an A500.

Soldered jumper wires are required to get full 2MB.

Revision 3 Amiga 500 machines require a capacitor mod to the memory board. Revision 5 PCBs were improved so the mod is optional. The capacitor mod duplicates additional filtering Commodore added to revision 6A and later Amigas. I can prefit this capacitor if you have a revision 3 Amiga 500 - contact me before ordering.

Amiga Model Memory Board Memory Board
+ Gary adapter (Kick v1.3+)
Memory Board
+ Gary Adapter (Kick v1.3+)
+ Jumper wire (ECS/1MB Agnus)
A500 rev 3 0.5MB slow 1.5MB slow not compatible
A500 rev 5 0.5MB chip/slow 1.5MB slow 0.5MB chip + 1.5MB slow
A500 rev 6A 0.5MB chip/slow 1.5MB slow 0.5MB chip + 1.5MB slow
A500+ rev 8A 1MB chip not compatible 1MB chip + 1MB slow

 

Real Time Clock (RTC)

Amiga 500

A RTC chip and battery can be fitted to the memory board.

The chip is an Epson RTC72421A or RTC72421B. Either will work but the A has a more accurate clock.

The clock battery is a standard CR2032 coil cell which will last 3 to 5 years.

Amiga 500+

The Amiga 500+ comes with an RTC factory fitted on the motherboard.

The original batteries are prone to leak which corrodes and damages the Amiga. Remove the original battery or replace it with a remote pack/coin cell mod.

Features

  • Basic memory board replaces Commodore A501 or A501+
  • Optional Gary adapter for 1.5MB or 2MB modes
  • Can provide extra chip RAM and extra slow RAM
  • Socket for battery backed RTC upgrade for A500
  • Low power & heat - negligible stress on the power supply

Kit Contents

The memory board, Gary adapter kit and RTC are available separately.

The full kit includes:

  • 2MB memory board
  • Gary adapter kit
  • Printed step by step instructions

The Gary adapter kit includes:

  • Gary adapter board
  • Connecting cable
  • Jumper wires (for full 2MB)
  • Printed step by step instructions

Where to buy?

The modules are available for sale on eBay or direct through this website.

Contact me for more information