Dead Test Cartridge


Availability: 2 in stock

SKU: vic20-dead-test Category:

Dead Test Cartridge


Dead test cartrige for the Commodore VIC-20 which is used to test the VIC-20 RAM and ROM’s.
PCB has a gold plated edge connector to ensure better connectivty into the VIC-20 expansion slot.
The memory testing routines are based off the code by Simon Rowe. I have updated the original code and added NTSC/PAL compatibility, ROM detection/verification and faulty chip identification.
When powering on the cartridge it will detect if you are using PAL or NTSC and set the appropriate video modes. Tests will then be run on the lower RAM, followed by video RAM.
(There is a bug in the diagnostic code that causes the text to appear in strange colours on NTSC versions – although the diagnostic tests still function. This does not effect PAL versions)
Lower RAM $0000-$03FF
Video RAM $9400-$97FF
Following that the onboard RAM on the cartridge will be tested:
  • 1Kb Expansion $0400-$07FF – RAM1
And then the main RAM on the VIC-20
  • Main RAM address $1000-$13FF (1Kb) – RAMa
  • Main RAM address $1400-$17FF (1Kb) – RAMb
  • Main RAM address $1800-$1BFF (1Kb) – RAMc
  • Main RAM address $1C00-$1FFF (1Kb) – RAMd
On each 1Kb of RAM the upper and lower nibble of data is checked, followed by address and data lines. If the test fails on the nibble then data/address lines will not be tested and the code will then move onto the next block.
If there is a fault found with any of these tests, a error will be displated along with the suspect chip ID.
Following these tests the CRC value is calculated for each ROM (Basic, Char, Kernal) and if a matching version is found the status page will be updated.
The code currently checks for:
  • 901460-02
  • 901460-03
  • 901486-01
  • 901486-02
  • 901486-06
  • 901486-07
Interpreting the output
When testing the main RAM, its broken down into 4 tests
  • Upper nibble
  • Lower nibble
  • Address lines
  • Data lines
The below result shows a lower RAM failure and no further tests are performed. 

The below results shows:
  • Upper nibble from RAMa (1000-$13FF) passes
  • Lower nibble from RAMa (1000-$13FF) fails with chip reference shown
  • ROM versions are calculated with CRC and shown

The below result shows:

  • Upper nibble from RAMa (1000-$13FF) passes
  • Lower nibble from RAMa (1000-$13FF) fails with chip reference shown
  • Upper nibble from RAMc (1800-$1BFF) fails with chip reference shown
  • Lower nibble from RAMc (1800-$1BFF) fails with chip reference shown
Always make sure the compter is powered off when adding or removing the cartrige. Take note of the correct oritentation of the cart before turning on your VIC-20


Dead Test Cartridge screenshot

Weight 60 g