Boot cartridge on 60Hz...

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Por Serkun123

Resident (48)

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15-12-2018, 13:09

Hi! I'd like to boot a Konami cartridge in 60Hz on a European MSX (50Hz by default). Is there a way to do this?

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Por Meits

Scribe (5484)

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15-12-2018, 13:20

Two ways I can think of right now:
- (Let someone) replace the ROM that does the boot-up stuff so your computer always starts at 60Hz.
- Have a slot expander with switches. Boot with the slot switched off. Switch on in Basic. Switch to 60Hz. Start cartridge.

Coming to think of it, there was something with a megaflashrom. Not sure, but I kind of remember there was a solution with that cartridge in slot 1 switching the computer to 60Hz and exectuting the cartridge in slot 2.

Por Grauw

Ascended (8381)

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15-12-2018, 14:06

Yeah, you can have a flash cartridge in slot 1 with a ROM loaded which just switches the frequency to 60 Hz, and then the game you want to play in slot 2 will boot up after.

Por Jipe

Paragon (1366)

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15-12-2018, 14:46

Por Eugeny_Brychkov

Paragon (1088)

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15-12-2018, 16:44

This is good question if it works (I hope it is). Imagine cart in slot 1 changes VDP reg 9 changing bit 2 (switching to another mode, PAL or NTSC) and also writing to specific register mirror in the upper RAM. But when game performs screen initialization (e.g. changing to SCREEN 2) will it reload default contents of R#9 from ROM?

How does it work, and how to properly achieve the goal?

GR8NET is having boot up menu, available when GR8NET initializes. I can put another item into the menu - changing refresh rate. Seems to be useful, but I need to be sure I do it right Smile Need to play with it a little. As I recall the best test is Aufwiedersehen Monty as it has continuous music, and I do not like it in 50 Hz mode!

Por Grauw

Ascended (8381)

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15-12-2018, 17:04

No reason why it shouldn’t work…

Games do not overwrite R#9 without regard. They will load the current value from the mirror, modify the bits they need to, and write it back, that’s how it should be done. If they wouldn’t do this they would force the frequency of the system away from the default when inserted in either a Japanese or a European system and cause display issues. (And then there wouldn’t be this question to begin with Smile, because the Japanese games would all run at 60 Hz on our European systems.)

p.s. R#9 is a V9938 register so MSX1 games will definitely not even touch this.

Por Eugeny_Brychkov

Paragon (1088)

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15-12-2018, 17:08

Then I have an issue. For some reason, which I did not document properly in my sources, I write 02h into R#9 in my ASCII-8 version of Auf Wiedersehen Monty (forcing PAL mode for V99x8). I suspect the same issue exists in Venom strikes back and Death Wish 3. Most probably I was assuming that these games were initially designed for 50 Hz mode on their original platform (thus slower play process). I did not have any bug reports back stating composite display issues, and it may only mean that none uses those ROMs Sad

Por Grauw

Ascended (8381)

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15-12-2018, 17:18

But Auf Wiedersehen Monty is a cassette game, and an MSX1 game too…

Sounds like whoever converted it to ROM wanted to insist it run on 50 Hz on Japanese MSX2 systems (assuming they use RGB and thus have no display issues). Well, for those cases it can’t be helped, of course. It’s definitely not common practice to do this in commercial ROM releases.

One thing worth noting is that at 60 Hz a display frame takes 16.7 ms while at 50 Hz it takes 20 ms, so a vsync-locked game designed for 50 Hz may not always run well at 60 Hz. But I don’t think there are many of those, and in this case we’re talking about games designed for 60 Hz, so there’s no problem anyway.

Por Eugeny_Brychkov

Paragon (1088)

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15-12-2018, 17:19

Grauw wrote:

Sounds like whoever converted it to ROM

I converted it, and you can find it here. I removed this setting, as well as detection of the VDP type as now it does not matter (I was detecting the VDP for solely setting R#9 to 50 Hz). Will do the same for Death Wish 3 and Venom Strikes Back.

Por Grauw

Ascended (8381)

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15-12-2018, 17:24

Considering that MSX1 systems have no means to switch the display frequency, I think forcing 50 Hz is probably never a good idea since it would only work on MSX2 and up anyway (and then cause composite signal issues).

Though offering a frequency selection choice to the user is nice I think, because I personally always did appreciate 60 Hz more than 50 Hz. So having such an option in the GR8NET boot menu sounds like a good idea. The MegaFlashROM SCC+ SD also has such an option in the OPFXSD ROM loader.

Por Eugeny_Brychkov

Paragon (1088)

Imagen del Eugeny_Brychkov

15-12-2018, 17:35

Thank you very much. I rebuilt all three ROMs, and uploaded onto the server.
I will build this option into the GR8NET's boot menu.

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