"Computer Space" rom on 31khz monitor,custom video mode/scaler settings needed.

bugwhacker
Posts: 14
Joined: Fri Oct 02, 2020 10:35 pm

"Computer Space" rom on 31khz monitor,custom video mode/scaler settings needed.

Unread post by bugwhacker »

This rom doesn't have a scan doubler setting in the menu and I have tried "forced_scandoubler=1" which allows me to play most other 15khz games just fine.

Is there a custom video mode that will allow this game to play on my 31khz monitor? Right now it displays mostly correct but the horizontal is shifted until the edges of the screen meet in the middle of the display.

I am using direct video over a dac

Thanks in advance for any insight.
bugwhacker
Posts: 14
Joined: Fri Oct 02, 2020 10:35 pm

Re: "Computer Space" rom on 31khz monitor,custom video mode/scaler settings needed.

Unread post by bugwhacker »

VGA20 RESOLUTION

HORIZONTAL VERTICAL
Scan Frequency: 31.55 KHz Scan Frequency: 70.0 Hz
Scan Period: 31.7 µSec Scan Period: 14.3 mSec
Active Video: 25.6 µSec Active Video: 12.2 mSec
Video Delay: 5.7 µSec Video Delay: 1.1 mSec
Sync Pulse: 4.0 µSec Sync Pulse: 0.2 mSec
Scan Line: 634 Pixels Screen: 450 Lines
Resolution: 512 Pixels Resolution: 384 Lines
Clock Freq: 20.00 MHz


I think this is what my monitor is looking for but I don't yet know how to turn it into a custom mode line.

I am trying to learn how to do the custom video modes per core but I am not having much luck finding a tutorial for it.
bugwhacker
Posts: 14
Joined: Fri Oct 02, 2020 10:35 pm

Re: "Computer Space" rom on 31khz monitor,custom video mode/scaler settings needed.

Unread post by bugwhacker »

So I am trying to work my way through this-

Modeline "512x384_70.00" 17.92 512 528 576 640 384_70.00 385 388 400 -hsync +vsync

PIXEL_CLK = 17920
H_DISP = 512
H_FPORCH = 16
H_SYNC = 48
H_BPORCH = 64
H_SYNC_POL = 0
V_DISP = 384_70.00
V_FPORCH = 1
V_SYNC = 3
V_BPORCH = 12
V_SYNC_POL = 1
INTERLACE_ENABLE = 0

video_mode=512,16,48,64,384,1,3,12,17920

Does this seem correct?
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jrronimo
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Re: "Computer Space" rom on 31khz monitor,custom video mode/scaler settings needed.

Unread post by jrronimo »

I know this is a bit of an older post, but were you able to get it working?

I've been looking at modelines a lot lately, and I've been using this post as a guide. Specifically:
-Modelines
The popular Xorg "Modeline" format can be converted to MiSTer video_mode strings :

Modeline "Name" Pixel_Clock HDISP HSYNCSTART HSYNCEND HTOTAL VDISP VSYNCSTART VSYNCEND VTOTAL
Becomes:
video_mode=HDISP,HSYNCSTART-HDISP,HSYNCEND-HSYNCSTART,HTOTAL-HSYNCEND,VDISP,VSYNCSTART-VDISP,VSYNCEND-VSYNCSTART,VTOTAL-VSYNCEND,Pixel_Clock*1000
I'm guessing you saw the same post, since the video_mode you wrote down seems correct.

For each core, you can define a section in the mister.ini. If it were the SNES core, it would be:
[SNES]
video_mode=512,16,48,64,384,1,3,12,17920
bugwhacker
Posts: 14
Joined: Fri Oct 02, 2020 10:35 pm

Re: "Computer Space" rom on 31khz monitor,custom video mode/scaler settings needed.

Unread post by bugwhacker »

I was able to get it working by moving to an analog video card instead of trying to do it over direct video with a DAC. I was then able to apply the proper video mode which needed to have the front porch timings changed to sync properly. This was done for a stand alone ComputerSpace machine and I didn't write down the timings but I can get them again sometime if their is an interest.
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