Re: How to create a freezer cartridge?

From: Ruud Baltissen (
Date: 1999-03-18 22:10:14

Hallo Tod,

> Yes, the Transactor had those articles and they were quite mind-bending
> and informative. I have those Transactors, but they didn't discuss the
> topic of FREEZING. I would like to know how this part is accomplished.
> Maybe I need to dig deeper into these articles.

I have once tried to copy a FC3 but stopped this project due to the fact that I 
got two others for free.

What I remeber is this. Pushing the freeze button caused an interrupt but also 
took care of the fact that the C64 read the NMI-vectors out of the EPROM of the 
FC3 instead out of its own Kernal. This trick was done by ONLY negating the 
-GAME line. As your own PRG is now in control running in the extern EPROM, 
nothing can disturb the contents of RAM and most I/O registers.

Groetjes, Ruud

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