Re: C128 diagnostic test cartridge

From: Nicolas Welte (
Date: 2002-06-10 10:31:35 wrote:
> I have never seen a diag cart for the C128. Do you know what it tests for
> which doesn't rely on the cables /dongles? Most of the ports would be

The bad thing is that the test program stops as soon as one test fails, but
it starts out with RAM, Z80 and VDC tests, and then fails with IRQ test on my
PAL 128D.

One extra port test I found is for the fast serial port, and there is also a
wire to the video port. Maybe it connects to audio in. I'll have to check out
all those dongle conncetions sometime.

> testable with a C64 diag kit, I'm wondering whether the EPROM is useful for
> testing C128 functions such as the extra RAM, MMU, VDC etc. Do you know
> where the EPROM maps to and the activation mode (I really don't know much
> about these modes on the C128, but assume it is treated as external ROM with
> GAME/EXROM now as outputs rather than inputs?)

It looks like it just maps in as an external ROM at $8000, but it might be
possible that it also runs from the internal ROM socket. Just connect the
EPROM to the data and address lines, connect the EPROM's /CS to /ROML and
leave /GAME and /EXROM alone. That should do. The Commodore REUs offer such a
socket, but it's also easy to make from any C64 EPROM cartridge (connect the
extra address line and open /GAME and /EXROM).

> What do you suspect the NTSC vs PAL quirk is?

I'm not sure anymore it fails due to PAL/NTSC differences. I tested it on
another PAL machine now, and that one passes the IRQ test, but then fails
with the ROM test. I'd have to install a US ROM into a PAL machine to see if
that works ...

So the ROM is nice, but it had to be changed to do the following things: 
- accept all ROM versions
- proceed when a test fails


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