X68000 Core On 15KHz TV?

[cyllboy]

I'm trying to get the x68000 core to work on a 15KHz tv via scart rgb. I think that the original computer had the capabilities to output on such display.

I believe that the core outputs 800x600 natively, but I could have got it wrong.

Can somebody help me?

Thank you in advance!

[zakk4223]

The x68000 core written by puu does not output native resolution, it is locked to 800x600@60hz.

Maybe you can turn on the vga_scaler over analog output and find a video mode for 240p? I'm not sure.

[akeley]

Interesting, I wasn't aware it could display 15Khz. Probably the only way is to open an issue on git and hope somebody will resume working on this core again some day.

[callanabrown]

If you have a GBS upscaler you can try the 15 Khz downscale option in the custom gbs-control firmware.

[vgesoterica]

I need to play around with the X68000 core more. It's the one original hardware platform I dont want to pay the price of entry to get into

[_javi_]

Although puu said he wont update the core anymore, maybe another dev could make this possible.

x68000 on CRT TVs would be awesome!!

[ash2fpga]

I was under the impression the x68k was being worked on.

https://twitter.com/_atrac17/status/1396706647444234244

https://github.com/Kitrinx/X68000_MiSTer

[softtest9]

While the X68000 is capable of outputting 15khz, this is software-dependent. A lot of games and other software, including the Human68k command prompt, use a higher resolution. Even games that you might think are 15khz sometimes turn out to have been line-doubled on real hardware. So while I'm hoping that the core's internal scaler eventually gets ripped out in favour of MiSTer's own scaler, this on its own will not make the core safe for use on a CRT TV. You would have to make sure that the higher resolutions are downscaled or displayed as interlaced.

[kalach.x]

I managed to run Sharp X68000 core on my PVM 14M2E using these settings

Code: Select all

[X68000]
vga_scaler=1
forced_scandoubler=0
vsync_adjust=2
video_mode=1536,180,152,274,256,1,1,16,34900
video_mode_pal=1536,180,152,274,256,1,1,16,34900
video_mode_ntsc=1536,180,152,274,256,1,1,16,34900

The _pal and _ntsc settings are not necessary but I had the same setting in default section.
These work with 60Hz force option in X68000 core.

I also needed to reconfigure one of the PVM mode (let's say there are four normal, U/S, 16:9 and U/S 16:9 - U/S stand's for under scan) to display proper height. PAL and NTSC on PVM need separate adjustments so I set normal mode for NTSC, u/s for PAL, u/s 16:9 for Amiga (it is quite tall...) and now normal 16:9 for Sharp.

BTW. This video mode is not ~15.7KHz but as much as ~16.4KHz and needed some v-hold adjustments and generally a) may not work b) my break your monitor/TV c) may not work properly with all games given X68000 liking to use different resolutions in different games.

So far I tested it with Akumajou Dracula and Bomberman. Both have resolution of 768x256. Scaler when no filter is used just drops exactly every 2nd line. It is not perfect solution by any means but seems to work better than playing Sharp games on VGA CRT or HDMI devices : )

IHBXn9uh.jpg (115.62 KiB) Viewed 20360 times

ps. I once notices tear line in the middle of the screen. Fiddles with options and it was gone. Gonna seek better solution for this for sure including maybe just dropping every second line and drawing them slower but this will require a lot of effort and for quick solution this one work's quite well.
ps2. Horizontal frequency could be lowered by dropping few backporch lines but I didn't wanted to have whole screen without any cropping.

[Pepeart]

I need some help, I need an explanation of what each digit means "video_mode_ntsc=1536,180,152,274,256,1,1,16,34900" this config its very close to work on my pvm, and I want to play with different values. Thank you in advance

[Yim]

From mister.ini:

custom mode: hact,hfp,hs,hbp,vact,vfp,vs,vbp,Fpix_in_KHz
video_mode=1280,110,40,220,720,5,5,20,74250

What each actually means (roughly):
hact is the horizontal resolution of the active display area (the bit you want to see)
hfp is the horizontal front porch - a blank signal that follows the active display
hs is horizontal sync - the time when the beam is moving back to the start of the next line
hbp is horizontal back porch - a blank signal before the active display
vact,vfp,vs,vbp are the same things but vertical
Fpix_in_KHz is the pixel clock: the total number of pixels per frame (sum of the horizontal components multiplied by the sum of the vertical components), multiplied by the frame rate and divided by 1,000 (to convert from Hz to KHz).

In the example given in mister.ini, Fpix is (1280+110+40+220=1650) x (720+5+5+20=750) x 60 (frame rate) / 1,000 = 74250

For the video mode you listed, the formula is

(1536+180+152+274=2142) x (256+1+1+16=274) x frame rate /1,000 =34900

So the frame rate is about 59.46

How you apply that info to get it working on your screen, I dunno.

[GhostofSparta]

Hi,

I am not sure if it is possible, but maybe someone here could answer my question? Is it possible to run the X68000 Core with analog output to the Retrotink 5x on an LG OLED 48C2? Or do I have to use the direct HDMI-Connection from the Mister to the TV?

Thanks a lot in advance!

[FoxbatStargazer]

Its *probably* possible but you will get cleaner results using the HDMI signal. There's not really anything the Tink5X does that the Mister scaler can't. That goes double for this core where the analog output doesn't seem to display cleanly on actual CRTs. Especially with the weird 55hz this core loves, you might need freesync on for your C2.

also a word of warning for the C2s: stick to 16:9 resolutions, so basically, 1920x1080 (mode 8). Any other aspect ratio (like 1920x1440) will cause frames worth of extra lag.

[GhostofSparta]

Ok, thanks for your reply!
Right at the moment I get a picture that seems to be squeezed to the upper half of the screen.

So, Freesync on my C2 has to be on, ok.
Do I have to change any settings on the Mister itself or is it possible to get the full screen size by changing settings on the RT5X (Output 1920x1080?, H.Sampling, etc)? It's a little bit weird because there are so much options to change settings right at the moment and I don't really know which one to choose.

Maybe you could tell me which settings I exactly have to change on either Mister or RT5X? That would be of great help to me! Thanks a lot in advance!

[FoxbatStargazer]

I don't have an RT5X so I can't tell you what needs to be done going that route.

For using Mister's hdmi output, in the ini you need video_mode=8, vrr_mode=2, vsync_adjust=2, vscale_mode=0. In the x68000 core menu I would change refresh from 60 to original, and use scaling v-integer maybe.

[GhostofSparta]

Alright, thanks a lot for your settings! Let's see if I could make the Core working with my setup!