Sharp CZ-604D-BK - Can someone confirm REAL 24 kHz support?

[luxml1]

Hello everyone,

I recently repaired a Sharp CZ-604D-BK monitor and I am trying to understand if it is REALLY a tri-sync monitor (15/24/31 kHz) or only a dual-sync 15/31 kHz model.

I am NOT looking for information copied from websites or old advertisements.

I would like an answer only from someone who actually owns this monitor and has tested it personally.

My observations:

15 kHz locks perfectly.
31 kHz locks perfectly.
24.8 kHz never locks.
The monitor stays in the same relay state as 15 kHz.
Horizontal frequency remains around 17 kHz instead of switching to the high scan range.
The chassis contains MC14040, 74LS26, MC14066, TA7630P and one unknown IC.

So my question is:

Has anybody personally tested a Sharp CZ-604D-BK with a real X68000 or another genuine 24 kHz source and confirmed that it can lock at 24 kHz?

If yes, I will continue troubleshooting.

If not, maybe this monitor is actually a dual-sync model or there are different chassis revisions.

Thank you very much!

[SuperDeadite]

That was one of the dual sync (15/31) only "budget" monitors. The more expensive models are proper 15/24/31 trisyncs. There are a few X68K games that support 24khz. Fantasy Zone, Marble Madness, Dragon Knight 3 and 4, and the recent Beep Falcom ports.

[fernan1234]

If you're only hooking up an X68000, there's no real benefit to running any games in 24khz mode. They will look better either in 15khz or 31khz anyway. Games supported it probably with 15/24 dual sync monitors in mind. If you have other retro japanese PCs you want to use then this monitor may not be ideal.

[luxml1]

Thank you very much!

This is exactly the information I was looking for. You saved me from spending more time chasing a non-existent 24 kHz mode.

Much appreciated!

[SuperDeadite]

If you're only hooking up an X68000, there's no real benefit to running any games in 24khz mode. They will look better either in 15khz or 31khz anyway. Games supported it probably with 15/24 dual sync monitors in mind. If you have other retro japanese PCs you want to use then this monitor may not be ideal.

This is completely incorrect. The X68000 boots in 31khz only and then software can change video mode. The OS itself does not support 15 or 24. A 15/24 dual sync monitor would be completely useless on X68K...

Games that actually do support 24khz on X68K are best played in this mode as it is their native setting. Most of them are ports of PC-88/98 games. When played in 24khz, they are dot by dot correct with the originals. In 31khz mode, they get a big black border around the image to deal with the unused pixels.

Fantasy Zone was 15khz in the arcade, but the original resolution couldn't be done on X68K in 15khz nor 31khz mode. Dempa used 24khz to force the pixel count to be dot by dot perfect. The manual even talks about this as the dev team was quite proud of pulling it off. Marble Madness also looks best in 24khz, no questions asked.

Claiming a 24kz native release will look better with a big black border is flat out bullshit. In the end, the list of 24khz games on X68K is small enough that many users won't miss it, but that does not negate the facts. If 24khz is supported, it is the best choice.

[orange808]

Analog monitors allow us to mechanically adjust underscan and overscan without digital scaling. I doubt any remaining "boxing" beyond the limits of the monitor's flexibility will be a big deal.

It's a CRT.

[SuperDeadite]

Analog monitors allow us to mechanically adjust underscan and overscan without digital scaling. I doubt any remaining "boxing" beyond the limits of the monitor's flexibility will be a big deal.

It's a CRT.

Doing so will greatly degrade image quality. Ask anyone that owns Gradius IV pcb what happens if you run it in 15khz mode and force stretch it to fill the screen...looks like crap.

[orange808]

Analog monitors allow us to mechanically adjust underscan and overscan without digital scaling. I doubt any remaining "boxing" beyond the limits of the monitor's flexibility will be a big deal.

It's a CRT.

Doing so will greatly degrade image quality. Ask anyone that owns Gradius IV pcb what happens if you run it in 15khz mode and force stretch it to fill the screen...looks like crap.

That's a much larger adjustment than this, no?

[fernan1234]

Claiming a 24kz native release will look better with a big black border is flat out bullshit. In the end, the list of 24khz games on X68K is small enough that many users won't miss it, but that does not negate the facts. If 24khz is supported, it is the best choice.

You're technically right, but in practical terms I'd still stand by what you responded to (except the 15/24 dual sync monitor part, which yeah that would not work well given that the x68k boots in 31khz as you noted).

If you have ever used a CRT that supports mid-res/24khz from Japanese retro computers I'm sure you've noticed that those are also displayed with black borders around the visible picture. Of course, you can use raster adjustment on the CRT to make it fill the screen, just like you can with 31khz signals, though different games will often require different adjustments. As for games that support both 24khz and 31khz, it will also be case by case, both based on the game and based on the CRT monitor you're using, which mode will work better. Using a modern scaler with a flat panel would probably offer additional solutions.

The point we can converge on however is that, for an X68000, 24khz is rather inessential. As for PC-88, most games look much better in 15khz mode anyway, but I'd say PC-98 old models is when you really want to have 24khz support. A few games for FM77AV would be another case.

[orange808]

Using a modern scaler with a flat panel would probably offer additional solutions.

Better is purely subjective. Depends on what OP wants.

If there's an option to introduce another machine to the video chain, OP could use a line doubler, instead... and keep the monitor as is.

The only complaint there is "too thin" scanlines, but it's going to be less apparent than it would be with 15kHz.

[SuperDeadite]

Claiming a 24kz native release will look better with a big black border is flat out bullshit. In the end, the list of 24khz games on X68K is small enough that many users won't miss it, but that does not negate the facts. If 24khz is supported, it is the best choice.

The point we can converge on however is that, for an X68000, 24khz is rather inessential.

I have already stated as such, several times. Most users will not need it.
But, the same could be said for 15khz, as roughly 80% of X68000 games do not support 15khz.
Most people will tell you 15khz is essential because the Capcom games boot into 15khz, but the reality is that there are only 5 Capcom games.

I have owned my XVI for well over 10 years now, and while I have experimented with flat-panel displays via XPC-4, I always came back to CRTs.
The OP clearly wants to use his original Sharp monitor, not any kind of scaling so that topic doesn't matter here. Last year, I played through the X68K port
of Xak II. It looks much nicer in it's native 24k over the default 31k setting. Like most NEC ports, the game uses heavy dithering due to lack of colors,
and when I tried stretching the windowed 31khz mode to fullscreen, it broke the color blending illusion that dithering means to create.

The internet is absolutely flooded with misinformation about the X68000. From my experience, most of it comes from Amiga fans who truly
believe the X68K is "just a Japanese Amiga." The idea that X68000 had 24khz support so that users could connect their machines to classic
15/24khz only dual sync monitors... is for lack of a better word, stupid.

All I have stated is that when available, 24khz is the display mode that the developers wanted you to use. 24khz is how these games were developed, with forced
31khz being added for compatibility. Dempa went out of their way to take advantage of 24khz to make Fantasy Zone's pixel count dot by dot perfect. They did not need to do this, but they did it anyway.
Afaik, none of the games with 24khz support 15khz. All of them are 24/31 only.

Just a few years ago, Beep partnered with Falcom to port Ys I-III, Dragon Slayer, and a few other games from the PC-88 to the X68000.
These were not lazy ports, Beep wanted them to be as accurate as possible. As such, they all boot into 31khz for compatibility, but recommend using
the 24khz option for users who have compatible monitors as they are then 1:1 with the NEC originals.

[fernan1234]

I have owned my XVI for well over 10 years now, and while I have experimented with flat-panel displays via XPC-4, I always came back to CRTs.

I would not consider an XPC-4 a modern scaler at this point. What I have in mind is something like a Retrotink4K or an OSSC Pro. The former in particular can work wonders with 24khz and 31khz retro JP PC content. But yes, that is an aside, as the topic is about OP using the particular CRT monitor he has. In which case the answer is the same.