C64 test rom without cartridge?

[Gordon Fecyk]

The c16 and plus/4 can use a diag264 ROM without making a cartridge. Is there a similar diagnostic ROM for the C64 that I can replace the Kernal ROM with?

[hofster]

You can burn the Dead Test diagnostic ROM (781220) to an EPROM and replace the Kernal ROM with it. It is made to run from $e000.

http://blog.worldofjani.com/?p=164

It's not a full-blown diagnostic program. As the name implies, it's made to diagnose systems that won't start.

All other diagnostic ROMs that I know of runs from $8000 and requires that a Kernal is in place.

Edited October 9, 2023 by hofster
typo

[Gordon Fecyk]

This was the link I was looking for, even including a 23xx to 27xx ROM adapter circuit. Thanks!

[R.Cade]

There is no reason you couldn't make a replacement kernal that had the full diagnostic- it just needs relocated/reassembled. 

 

The dead test is only that way because it uses the Ultimax mode to get control and bypass the ROMs, and that memory map doesn't see all of the hardware.

 

However, 9.5/10 times the dead test is enough to diagnose the machine.

 

Edited October 10, 2023 by R.Cade