The Expert Cartridge – The expert among specialists


After the quite successful ISEPIC module, which was launched in 1985, a worthy successor followed less than a year later.

And since the ISEPIC cartridge was taken off the market again due to some pressure from the software industry, the Expert cartridge had an easy time becoming even more successful.

First distributed by Trilogic, the whole thing was later taken over by Cat & Korsh. There were different versions and hardware upgrades. Also the software for this module was maintained for quite a long time.

Because in contrast to many other representatives of these Freezer modules, the software was not stored on an EPROM hard disk, but was loaded from floppy disk. This made software updates very easy, since only the floppy disk had to be brought out again.

To make the card fit into a standard cartridge case, I adapted the replica accordingly.


As for the operation, this cartridge is a bit “special” and unfortunately not completely self-explanatory.

The instructions often don’t really help and confuse more than they clarify.

Basically, the operation is relatively simple, as long as you follow certain steps.

The procedure has always changed a little in the course of the different software versions. I used version 4.1 for my tests and describe my procedure.

The cartridge has two buttons and a switch with 3 positions. The left button is a normal reset button and the right one is for the mysterious “ESM” function, which also includes an LED.

What the ESM is supposed to be is not really explained. The button should also only be used when the LED is lit. However, I have not had this case yet. Looking at the schematic, this button seems to be intended to override any NMI protection mechanisms with it.

The switch has 3 positions. On the left is the programming mode, in the middle the card is switched off (but not completely) and on the right the card is “armed”.

The computer should always be switched on with the switch in the “OFF” position, i.e. switch in the middle. In the “ON” position the Commodore C64 gets “stuck” and in the “PRG” position sometimes too.

So switch off the computer, switch position in the middle, plug in the card and switch on the C64.


After that the program “Multi-Menu” can be loaded from the floppy disk and started. The following picture appears:

In contrast to the ISEPIC module, the software does not have any query whether the switch is in the correct position.

Sometimes it says at the beginning that the switch should now be set to the “PRG” position.

Ultimately, however, now is the moment to set the switch to the left and then press the space bar.

You can actually do everything that you normally do with your computer, except switching it off of course. Because then the card loses its software, which was just loaded into the RAM of the card.

Now, for example, a game can be loaded. If you then want to save the game, it is enough to simply press the <RESTORE> key (Which ultimately does nothing but trigger an NMI).

Sometimes the right button on the module also works. For me, however, this was rather rarely the case.

After that comes the following menu, which is again quite self-explanatory.


The board itself consists of a few standard components that should be easy to obtain.

I have uploaded the board at PCBWay, so that it can be ordered there quite simply:

The assembly is quite simple and there is nothing special to consider, so that the card should not cause any problems even for less experienced beginners.

I have attached the software below.

Components list

#ManufacturerPart NumberDescriptionQuantity
1TE Connectivity1-1825027-1SWITCH TACTILE SPST-NO 0.05A 24V2
2NXP Semiconductors1N4148NEXPERIA – 1N4148 – DIODE, 1N4148 AMMO-BOX 10K4
3E-Switch200MDP3T2B4M6QESwitch Toggle ON OFF ON DPDT Round Lever PC Pins 3A 250VAC 28VDC PC Mount with Bracket1
4Wurth Electronics151033RS03000WURTH ELEKTRONIK   151033RS03000   LED, 3MM,  RED, 2600MCD, 621NM1
5KEMETC315C101K5R5TACapacitor, Ceramic, 100Pf, 50Vdc, 10-% Tol, 10+% Tol, X7r-Tc Code, -15, 15%-Tc1
7YageoCFR-25JB-52-1KRES 1K OHM 1/4W 5% AXIAL1
8YageoCFR-25JB-52-1MRES 1M OHM 1/4W 5% AXIAL2
9YageoCFR-25JB-52-2K2RES 2.2K OHM 1/4W 5% AXIAL1
10YageoCFR-25JB-52-6K8RES 6.8K OHM 1/4W 5% AXIAL1
11YageoCFR-25JB-52-39KRES 39K OHM 1/4W 5% AXIAL1
12YageoCFR-25JB-52-47KRES 47K OHM 1/4W 5% AXIAL1
13HynixHY6264LP-15Statis RAM 8kx81
14ON Semiconductor / Fairchild74F00PC74F FAST TTL, 74F00, DIP14, 5.5V1
15Texas InstrumentsSN74HCT14NE4Inverters Hex Schmitt-Trigger Inverters2
16Texas InstrumentsSN74LS11NIC GATE AND 3CH 3-INP 14DIP1
17Texas InstrumentsSN74LS32NTexas Instruments SN74LS32N, Quad 2-Input OR Logic Gate, 4.75  5.25 V, 14-Pin PDIP1
18Texas InstrumentsSN74LS125ANIC BUS BUFF TRI-ST QD 14DIP1
19NichiconUMF1V010MDD1TPCap Aluminum Lytic 1uF 35V 20% (4 X 5mm) Radial 2.5mm 50mA 1000h 105C Ammo1


Expert Cartridge Utility Disk v4.1

Software for "The Expert Cartridge"

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