Hi,
there are tons of discussion about tricky msx1 vdp modes, some times referred as illegal modes.

Some of those mode can be used to achieve some special effects or behaviuor.

It's strange that this is only valid for tms* not for v9938.

Are there some tricked msx2 video modes that can be useful?

(such a hybrid sc4/5 mode where patterns are made up of screen 5 pixels, without color clash, will be superb!)

some one has tested this?

On MSX2 there're 5 mode selection bits and only 10 combinations are used (not counting the 2+ ones), maybe some of them could show some funny mode . However I think that someone wrote before about the deterministic way the MSX2 VDP use those bits, making impossible to get new combinations, I'm not sure as I've never tested it.

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On MSX2 there're 5 mode selection bits and only 10 combinations are used (not counting the 2+ ones), maybe some of them could show some funny mode . However I think that someone wrote before about the deterministic way the MSX2 VDP use those bits, making impossible to get new combinations, I'm not sure as I've never tested it.

May be the deterministic schema in only for msx1 compatibility modes...

2^5=32-10 = 22 available combinations to try...
the problems is test and interpretation to know if some mode could be useful...

I've took a look: modes of bit configurations in msx2 modes appear to have m1/m2 always = 0. Maybe playing with those bit could reveal some suprises.

Unfortunately i've not the way to test on real msx2 machines and emu's are not the right way to this kind of work.

Is there any that can run some .com programs i can make on the real machine and report me some results?

I can test the COM programs without problems.

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I can test the COM programs without problems.

thx, I will prepare some test.

Do you have a original v9938? (not 9958)

Good that you're doing the tests PingPong. I don't think you'll find the same behavior on the V9938 as on the TMS though. I've done some tests (nothing complete) and on the TMS each mode bit has a meaning (addressing, timing,...). On the V9938, the mode bits seems to be used only as an identifier for the screen mode, and each screen mode has its own implementation in the VDP. So unless there are some true undocumented modes you probably won't find anything new. Would be fun though and even if not, its good to know for sure.

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Good that you're doing the tests PingPong. I don't think you'll find the same behavior on the V9938 as on the TMS though. I've done some tests (nothing complete) and on the TMS each mode bit has a meaning (addressing, timing,...). On the V9938, the mode bits seems to be used only as an identifier for the screen mode, and each screen mode has its own implementation in the VDP. So unless there are some true undocumented modes you probably won't find anything new. Would be fun though and even if not, its good to know for sure.

I already know what you think about v9938 bits meaning, but i hope for msx2 modes the situation is different.

Notice: m1/m2 are always zero when working in sc4-8. My guess is what happening if i play with those?
...

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Do you have a original v9938? (not 9958)

Yes, both in fact...

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Quote: Do you have a original v9938? (not 9958) Yes, both in fact...

Good!
let me know where i can send the .com files, that tomorrow i will (hopefully) make.

Send them to my email, you can find it in my profile :-)

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Send them to my email, you can find it in my profile :-)

check mail....

Checked!. I'll try to do some tests this same night.


ummmm....I'm not gonna fry something, isn't it?

The results are pretty unexciting . With the 9938 all modes show similar pattern to the one in the photo, maybe with a bit more solid filling, following by a white screen that seems to remain till a key is pressed, then the next text stats screen appears and asks for a key being pressed.
The 9958 seems to vary a bit the behaviour, all modes are like the one in the photo (taken thanks to the PAUSE button). After showing that, there's no white screen and the text screens appears inmediately:



Hope this helps!

When i did this on openMSX my videocard started smoking.......

100% perfection!!!