The DIY Gmod2 / Magic Desk cartridge is a cartridge that is compatible to the well known Gmod2, Ocean or Magic Desk type cartridges, for the Commodore 64... and Commodore 128 as well.

A lot of Commodore software is still being written today and nowaday, often designed for cartridges. A bank switched cartridge offers a rather large amount of storage that is instantly available without loading, and also directly adressable, which means the Commodore 64 can execute code directly from cartridge. Games can access large amounts of graphics data, which was a lot harder with floppy disks in the golden days of the Commodore 64, let alone tapes. As a result content rich C64 games are being made, which is a new chapter in the already rich software catalog of the Commodore 64.

Popular formats in mass produced C64 cartridges are Magic Desk, Ocean and nowadays, Gmod2. This item is a DIY it that allows you to build these cartridges, but unlike the mass-produced cartrdiges, this cartridge is not designed for mass production purposes, but is rather aimed at hobbyists and developers.

In order to do so, the cartridge has been fully designed from through-hole components, that make it a lot easier to solder at home, and all integrated circuits can be socketed. This includes the flash-ROM, which can be easily removed and programmed in an EPROM programmer and reinstalled. In addition programming in an EPROM programmer, you can program this cartridge inside the C64. Programming the cartridge is possible from any Commodore 64. (The original Gmod2 cartridge has a minimal programming circuit which only allows programming inside the assy 250469 mainboard.)

In order to make the life of developers easier, the cartridge has an on/off switch, which will inhibit the C64 from booting the cartridge. This switch is usefull if the cartridge has been previously programmed and you would like to reprogram it, or just want to get into BASIC for e.g. development or debugging.This cartridge can be used to run games that are distributed via a digital download on real C64 hardware, but you need to get the files on C64 compatible storage media or use an EPROM programmer.

The actual cartridge formats supported are Gmod2, Magic desk up to 512KB, Ocean 128KB and 512KB. 256KB Ocean cartridges (which use the C64's 16K cart mode) are not supported and neither are 1MB Magic Desk cartridges.

The PCB is wired by default for Ocean and Gmod2 compatibility. An optional jumper J1 allows the user to easily rewire the cartridge in a Magic Desk mode.

Flash utility

Thanks to the use of through hole parts and IC sockets, you can very easily flash the cartridge in an EPROM programmer. Just take out the flash RON and program it with the programmer of your choice. The popular TL866 works great. However, one of the neat features of Gmod2 is that it can also be flashed from the C64.

A flash utility has been written in order to facilitate easy flashing of the cartridge from the C64. If you have a C64 storage medium that can carry 512KB files, this utility can flash the entire ROM in one sweep. If you happen to have storage media that are not large enough to carry 512KB files, the utility allows you to flash individual flash ROM sectors. For example you can split a 512KB image into 4 files of 128KB and store these on 4 1541 compatible floppy disks. Or you can use 2 256KB files and store these on 2 compatible floppy disks. The utility is flexible and leaves the choice upon you.

Download the flash utility here:

You should use the C64 flash tool for the C64 version of the cartridge and C128 version of the flash tool for the C128 version of the cartridge. You cannot mix and match.

The flash utility has been developed using CC65 on a Linux system, and thus the Makefile is optimized for such a setup. However, you should be able to get the software compiled on any system where you can install CC65. The petcat utility from Vice is also necessary to compile the source code.

Commodore 128 version

Many developers on the Commodore 8-bit platform are open for a Commodore 128 version of their creation with enhanced features. However, Commodore 128 developers also often encounter that they still need to invent the wheel, as the Commodore 128 native mode does not have as much infrastructure as the Commodore 64 platform.

Looking at cartridges, Commodore 128 developers will notice a complete lack of bank switched cartridges, these simply don't exist, preventing any cartridge releases for the Commodore 128 platform. The DIY Gmod2 Magic Desk cartridge is available in a Commodore 128 version and might well be the first bank switched cartridge available for the Commodore 128 native mode. The wheel has been invented, Commodore 128 developers now have a great cartridge available to release software on.

Magic Cartridge Generator by Žarko Živanov supports Gmod2 for the Commodore 128. It allows you to combine multiple .prg files into a cartridge and add a nice menu to it.

You can download technical information about the Commodore 128 version of the Gmod2:

Cartridge cases

The cartridge has been designed with two mounting holes, which makes it compatible with a range of available cartridge cases. The following C64 cartridge cases are compatible:

From left to right: Cartridge cases from The Future Was 8-Bit, Protoparts and Individual computers.

Obtaining a cartridge

I am selling the DIY Gmod2 Magic Desk cartridge on SellMyRetro. Please make your choice:

Commodore 64 version

Commodore 128 version

It is not mandatory to use Sell My Retro, if you don't like to create an account there. If you would like to buy directly, fill in the following form:

E-mail address:
How many Commodore 64 Gmod2 kits would you like to buy:
€15 per piece
How many Commodore 128 Gmod2 kits would you like to buy:
€12 per piece
How many cartridge cases would you like buy:
€5 per piece
You cannot buy more cases than cartridge kits.
Please assemble the cartridges for me:
€5 per cartridge
Your postal address:
(if you have a personal comment, you can write that here as well):

Shipment costs are at the moment €5 within EU, €6,50 Europe non-EU and €11 rest of the world.

At the moment I am using grey cartridge cases from Protoparts.

(The Commodore 128 cartridge has a slightly lower cost than the Commodore 64 cartridge as an incentive for Commodore 128 software development.)

There are no Gerber files: I fear that if I offer Gerber files for download, internet marketplaces will suddenly be full of pirated cartridges of modern Commodore 64 games. The Commodore 64 is one of the few retro computers that can sustain commercial software development, and this should be nurtured. Therefore there are no Gerber files for download. The DIY kit will be as good as it gets and is available at a friendly price.

People interrested to release their games on Gmod2 for mass production should contact Individual Computers. I do not want to become their competitor for mass production cartridges.


Do you have any questions or would you like to contact me for some other reason? You can e-mail me at daniel.mantione at freepascal dot org, or use the following form:
E-mail address:
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(C) 2021 by DaniŽl Mantione

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