Ah ok 🤣

So I programmed the EPROM chip, but I hadn't the time to take out my only MDA/CGA/EGA monitor to test if the card actually works ... Maybe I'll have the time thursday or the next week-end.

Scali wrote:

Deksor wrote:

https://m.youtube.com/watch?v=-eRvF0aSYlc someone managed to get composite colors with this chip

Yes, that's me, with my Commodore PC20-III.
I also did one with an ATi Small Wonder, but its colours are all wrong in the 16-colour mode: https://youtu.be/eRVwYCq8X5w

The colors in that video look suspiciously like the effects of a phase offset of n×90° between assumed and real NTSC color sub-carrier, namely swapped and/or inverted redness and blueness components.
You are apparently not the first one to run into that problem: https://youtu.be/BdhvIfmRtvQ?t=393
But since that version of Commander Keen is a mod, anyway, there is still hope.

EDIT: In this particular case, both, the redness and the blueness component, are simply inverted.

Bump.

Yeah a year has passed ... But anyways so after some tests, the card manages to display something, except it looks like this

Now this doesn't look normal at all. However I can recognise the text that's supposed to be there in that gibberish (like, when the DOS prompt is displayed, there's some gibberish on the left that is the same length as the DOS' prompt) so it works but it doesn't show the right things.

I doubt my flash is bad or that the ROM has the characters put at the wrong places though. This is the plantronics graphic mode and the same kind of thing happen but differently : .

This is supposed to be a black screen with a small green snake and randomly placed red dots. (This is my little asm project : [Game dev] Snake8088 (temporary name) and no it's not a programming error, this works well on my ati small wonder).

What's even weirder is that these green bars do not always show up and also that considering how my game works, that these bars are "physically" in the ram (my snake dies when it hits a green pixel, so when it hits a bar, it dies). At first I thought it was bad ram, but these photos have been taken after buying new ram and before that it was doing the exact same thing.

Now the card seems to react to the computer's activity to some degree (colors may change and some characters are changing in some spots when there's disk activity).

I don't have any other solutions now. What would you suggest to do next to save this card

If you are sure about the data integrity and data layout, then maybe it is a pinout problem.
27C256 EPROMs and 28C256 EEPROMs, for instance, have a slightly different pinout. Not different enough to destroy the chips, but different enough to result in garbled output.
I made that mistake with a homebrew Gameboy cartridge a couple of years ago.

Yeah but this is the eprom the card came with, and it shouldn't do anything in graphic mode.

Actually, it seems that the last bit is turned on constantly in RAM (looking at the ASCII table, "@"'s code is 1000 0000, and in plantronics mode that means that every 4th pixel will be a bright green colored pixel which corresponds to the pattern I can see).

Something must be off between the RAM's output and the PVC4 chip.

Did you test the RAM chips? And did you check the data lines, if you think that one bit is always 1....
I see two bodge resistors near the RAM chips. Where do they lead to?

I believe the ram chips are good because I ordered two new chips and the problem is identical. As for the data lines, I haven't checked them yet.