M-1024C cartridgeOr how to get 16 M-64C on your JX10/MKS70... Getting a M-64C these days is pretty difficult, and prices are high on the various 2nd hand sites. Buying them new is of course impossible. With the new assigner code, it is possible to do many things, and amongst them, control a better and newer cartridge, so I decided to create a 16-banks M-1024C cartridge, using modern chips and without requiring any modification to the JX. The cartridge is also compatible with other Roland devices (tested on MKS80), but obviously seen as a simple M-64C.
And here we are, after many hours spent debugging a hardware issue (see below), the cartridge is now working perfectly.
Selecting a bank can be done manually or over midi. Manually, press “recall” (JX10) or “value”(MKS70) followed by a patch button (A-H, 1-8) and one of the 16 banks is selected. At the same time, a midi control message is sent. Using midi, sending the control message will select a bank, assuming that the message is valid.
Under the “write” menu, it is possible to copy a bank to another one.
Ordering and availabilityThe cartridges are now available, but in limited quantity (red numbers below). The following options are available:
-  Trade your cartridges : send me 2 complete cartridges (M16C or M64C), get one M1024C cartridge (0€)
-  PCB (all components soldered, tested) : you need to find a cartridge to get its box and connector, and solder the PCB to the connector. (69€)
-  Upgrade your cartridge : send me a complete M16C or M64C, and get one M1024C cartridge (149€) [Free 3.0x upgrade if required]
-  Cartridge M1024C, ready to use (199€). [Free 3.0x upgrade if required]
Technical detailsThe cartridge is made of a 128K SRAM chip. These modern chips are much faster than the older 2K chips used by Roland. Usually, a faster chip is better, but in this case, it wasn’t. The reason was root caused to an errata of the 6303 CPU (a glitch can happen on some signals), and the fast sram was affected. This is shown below (yellow trace). Extra circuitry has been added in the new cartridge to workaround this errata. Finally, a GAL controls the upper 4 address lines and the JX assigner generates a particular sequence to program the GAL. This is fully transparent to the user, and the cartridge appears as being 16 M64C in a single package.
Testing the new cartridges is done using a USB JX cartridge reader, shown below.