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Color Classic VGA Mod. the CORRECT way

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Also, it shouldn't be possible to do 640x480 @ 16-bit. That would be 614.4k of VRAM. The most you can have in a CC is 512k. How does the system handle the difference in available vs. needed VRAM? Does it dip into system memory? Is it even capable of doing that? It doesn't seem likely, since the default video modes for the CC all fit easily within the maximum available VRAM.

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On 4/10/2019 at 1:53 PM, Paralel said:

Also, it shouldn't be possible to do 640x480 @ 16-bit. That would be 614.4k of VRAM. The most you can have in a CC is 512k. How does the system handle the difference in available vs. needed VRAM? Does it dip into system memory? Is it even capable of doing that? It doesn't seem likely, since the default video modes for the CC all fit easily within the maximum available VRAM.

I have upgraded this guy to a Color Classic II logic board(couldn't stand the gimped stock CC performance) and with the 256K expansion I have 768K VRAM.

 

As for screen distortion, it's the photo and I'll try to get a better one. I'm upping the dissipation rating of a resistor that is dissipating too much at the moment and when that is done I will get better photos. It does curve a bit at the top of the screen but it appears to be normal as it did it before on another analog board and is also something I notice in photos of other machines.

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I thought I'd add this little update. This mod seems to be working just fine so far on the Rev D board outside of a warm reboot sync problem that I can't trace. None of the ICs or resistors, outside of the really hot area below, get above ~115F so it shouldn't be drift or anything like that. Leave the machine off for a few minutes and it syncs right up and works for hours without a problem. It just seems to need shut down, not powered off, so the problem is unrelated to RF11.

 

I upsized RF11 to a 3 watter and it runs at about 250F now but CF8 just runs hot I guess. That whole resistor/capacitor/zener diode area runs as long as the switch on the back is turned on so that electrolytic sits at about 65C(measured by attaching thermocouple). It's not comfortable to touch but well within specs, especially if you swap it out for a 105C during recap.

 

Considering undoing the mod as I don't like the lack of clarity at 640x480 compared to factory resolution. To each their own!

Edited by dkjones96

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Forgive a naive question, I have never tried modding a CC but am thinking about it - why is this method preferable to cutting the analog board trace, which seems much easier? Is it because we don’t like dremeling the analog board, or does the older method have problems?

 

I’m referring to this of course, “option 1”: https://powercc.org/640x480/

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