DesTestMAX by Factor of Matt

The DesTestMAX project aims to improve upon Commodore’s Dead Test cartridge by using a more comprehensive memory test strategy and provide easier to interpret diagnostic output.

DesTestMAX utilizes the MAX (or ULTIMAX) cartridge mode as it allows us to place code directly in the $E000-$FFFF block of memory that gets executed as soon as the system resets. Such a situation allows the DesTestMAX code to take complete control of the system right from the get-go. Unlike the regular Commodore 64 boot process, DesTestMAX makes very few assumptions about the state of the machine and can produce usable results even with a severely broken machine.

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.

The big drawback to MAX mode is that only the first 4K of system memory is available to the CPU. DesTestMAX then can’t be a fully-comprehensive memory test, but it can be a great help when faced with a Commodore 64 that shows nothing but a black screen.

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

DesTestMAX utilizes the March-B memory test algorithm which can detect a wide range of memory errors including bad bits and page errors. Good care has been taken to ensure that no assumptions are made about the validity of memory before it has been tested. Neither Zero Page nor the Stack are used before those two memory regions have

been verified since errors in either could cause havoc with the running code. The full 4K memory-test takes about 10 seconds and verifies all but the first 2 bytes of memory all in one go.

ROM Created by Matt Desmond – TFW8b is super proud to be an official distributor, even more so speaking as a C128 BBS’er that knows how good DesTerm128 is! ;D

Click here for Matt’s DesTestMAX (Desmond’s C64/MAX RAM Test Thing) page