The ‘Switch boots into MAX (or ULTIMAX) mode to perform the initial 4K memory test, then switches to 64K mode to test the full 64K of memory.  This arrangement allows the ‘Switch to work in a wide-range of situations.

The 6510 CPU, VIC-II and PLA need to be functional, though the ROMs, CIAs and SID are not required and can be removed if socketed.  See the C64 Hardware Considerations section for more details.

A DesTest MAX-Switch cartridge will also work in a Commodore 128.  DesTest MAX-Switch will automatically run in ‘64 mode yet requires the ‘128 kernal, a working Z80 and a working MMU.  The VDC is not required.

The DesTest MAX-Switch (or just the 'Switch) solution aims to fix this limitation!

The custom DesTest MAX-Switch cartridge adds the capability to switch (hence the name) between the MAX-mode and regular cartridge-mode under program control.  The new DesTest Software allows the following features:

• Full 64K memory test using the March-B algorithm.
• No dependence on the ROMs, CIAs or SID: they can be removed.
• ROM checksum verification (if installed).
• CIA TOD consistency verification.

The DesTest MAX-Switch hardware includes provisions for the following:

• Power LED.  Most of the time when diagnosing or repairing a C64, the keyboard is removed along with the Power LED.  The DesTest MAX-Switch cartridge includes a simple power LED to avoid mistakes like removing or inserting ICs with the power on.
• Reset Switch and LED.  A faulty reset-circuit in a C64 can prevent it starting-up properly.  A reset-switch can temporarily bypass a faulty reset-circuit and the LED gives a visual indication if something is wrong!