Re: [Fwd: Diagnostic cartridges]

From: Nicolas Welte (
Date: 2002-01-29 11:05:33

Marko Mäkelä wrote:
> What was the code you added?  Just a simple $100-$1ff memory test and
> then a jump to ($8000), where the cartridge would also be mapped?  I
> guess the cartridge will then complain about the KERNAL and BASIC ROMs
> and any RAM above $1000, as they are not available in the UltiMax
> configuration.  There are 1014 $aa bytes at the end of the 8k ROM,
> which is pretty much space for additions.

I'm pretty sure Nick simply switches back to the normal EXROM configuration
right after an initial startup sequence. I have a copy of his modified ROMs,
but didn't want to modify a Supergames cartridge. I think I'll add some logic
to a standard third-party 8k cartridge to achieve the same functionality. 

Recently I had some problems diagnosing RAM failures in two machines (one SX
and one C64A breadbox), because my normal diagnostic ROM did not come up at
all. I wonder if the KERNAL crashed because it relied on some RAM portions to
be okay, and if Nick's startup code would help in this case. I found another
solution then: I have a Lemans game cartridge that runs in Ultimax mode, and
it sometimes started up with a garbled screen. I was able to get an idea
which RAM chips are damaged by looking at the pattern on the screen :-) Of
course this would've been easier if the contents of the screen RAM are set to
all $00 or $FF, and this is what I'll do next time, I guess. 


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