N00b Alert – OSSC Layman Support Request

[Hardcore0bject]

Hi all,

New to FPGA/OSSC scene since my beloved B&O 21” CRT has recently given up on life. I’m not new to retro consoles and the varying resolutions they’ve put out over the years from 240p to 4K 50 – 144hz, however I’m not by any means familiar with the science behind understanding how these are put together and configured with timings/frequencies etc. I’m out of my depth here and need some guidance before I give up.

I dug out an old Samsung SyncMaster 743 which has a native 4:3 resolution and built in speakers, perfect for an Amiga desktop setup. I mainly play games but also do some tinkering around in workbench on an A500 Plus (ECS). I’m not looking to configure High resolutions out of workbench, my main priority is to get nice crisp pixels and scan lines coming out from it’s native resolution whist gaming off floppies. This is a PAL unit.

Problem is, and I’ve tried every setting in the OSSC and played around with lots of Adv Timings based on plenty of forum posts here, I just can’t get the monitor to sync correctly. Forget perfect pixel and correct masking etc, this monitor constantly shows up a ‘Not Optimum Mode / Recommended Mode 1280 x 1024 60Hz’ error for about 30 seconds and then goes blank until i change the monitor input source away and then back, or change the input source on OSSC.

I have an RGB scart from the Amiga going into the OSSC, then HDMI to DVI adapter into the monitor, I’ve changed the TX output to DVI, and will always get a picture of some kind, but not one the monitor reports it’s happy with and shuts off after each timeout. I’ve also now tried with an active HDMI to VGA adapter, slightly different images qualities and frequencies but ultimately same complaint from the monitor.

From everything i’ve read I’m sure the monitor may not support the resolutions the OSSC is putting out at the correct frequency. But really need your help to understand whether I’m wasting valuable effort on this monitor and should just get another. Supported resolutions of the monitor from manual are here – https://www.usermanual.uk/samsung/syncmaster-743em/manual?p=57

I’ve currently got the following settings applied in OSSC.

AV1_RGBS 313-p
15.62kHz 49.92Hz
TX output – DVI

Output Options:
240p/288p proc
Line 4x

Line 4x mode
320×240 optim ( My logic suggests 320 x 4 = 1280 ? )

Adv Timings:
Have played with these to no avail, can see picture moving around and at one point did see in the monitor menu it was receiving a 1280 x 1024 signal but still complains with a floating ‘Not Optimum Mode’ warning after a few seconds of not video change and then shuts off. I’ve now returned these values to default.

Any help to understand the science behind this would help. I’ve bought this OSSC to mainly setup a nice Amiga / 4:3 LCD desk based setup, but will gladly move the device over to my retro consoles connected to a Sony 40” LCD to get more value out of this device, if what I’m trying to achieve with the Amiga looks like a pipe dream.

Thanks in advance.

[Zacabeb]

My best guess is that the SyncMaster 743 doesn’t like 50 Hz, which is a common problem when it comes to computer monitors.

[BuckoA51]

Yes I’d say that was the case too, you can use different monitor drivers in Workbench to force the Amiga to output 60hz. OSSC can only multiply resolutions it’s fed in so in the case of Amiga, 320x288p x 4 = 1280 x 1152 ~ 50hz, not a standard VGA resolution.

You shouldn’t be using the optimal modes as Amiga is not outputting 320×240, stick with generic timings.

[Author]

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