Minimig (Amiga) core discussion

[sonycman]

Hi guys,
It seems that native video output of minimig (VGA) hardcoded to 28 MHz pixel clock, resulting in constant 640x480 (or similar) resolution.

Is this correct?

If so, could it be possible to send this video stream via HDMI 576p (without the scaler) as nearest resolution?
Should the active pixels area fit into 720x576 fine?

I'am just thinking about porting this core to another fpga board...

[Sorgelig]

Hi guys,
It seems that native video output of minimig (VGA) hardcoded to 28 MHz pixel clock, resulting in constant 640x480 (or similar) resolution.

Is this correct?

If so, could it be possible to send this video stream via HDMI 576p (without the scaler) as nearest resolution?
Should the active pixels area fit into it fine?

I'am just thinking about porting this core to another fpga board...

28MHz is a base pixel clock for Amiga AGA chipset. No idea how you come to conclusion it's able to output only single resolution. All Amiga resolutions are supported.
I plan to port Direct Video to this core as to all other cores. But it's mainly for analog conversion. Not every HDMI display accepts arbitrary pixel clock.

[sonycman]

Pixel clock is 28 MHz, is'nt it so?
So all it can do is 640x480 or near to it at maximum.

Amiga low resolution mode 320x256 and high resolution 640x256 fits in this good enough.
Don't know much of super high res 1280x256 though.

[sonycman]

Sorry, its not that easy to write in english for me...

What I wanted to say: amiga low res and high res video modes (scandoubled) should fit in to 576p HDMI resolution.

Super high res with 1280 pixels in horizontal lines needs 720p HDMI.

I'll start with the first two resolutions, as the most used.

[Sorgelig]

Resolution and pixel clock have no fixed relation. It depends which refresh rate it produces.
Super HiRes (1280x) is 28MHz
HiRes (640x) is 14MHz
LoRes (320x) is 7MHz
All of them are 240p60 or 288p50
or 480i60/576i50

There are higher custom resolutions but they produce low frame rate (45Hz, 40Hz, or even 10Hz) and require special monitor.
With scaler on HDMI all custom modes are available over HDMI and frame-converted to 50/60Hz.

[sonycman]

Thank you, Alexey, for an overview.

Did'nt you use built in minimig scandoubler?

I plan to not use any scaler at first, as I seen posts about it causes some flicker on interlaced frames.
So 576p is an optimal resolution for me (I'am talking about different board on which I want to port this core, not the Mister board).

And of the vertical frame synchronisation between HDMI and native core video output - to avoid frame tearing you implemented pixel clock alteration to match input frame rate.
Is that enough to perfectly sync frames or there must be additional fine tuning by altering amount of horizontal\vertical front\back porch pixels\lines in the real time?

Thanks in advance for any advice.

[Sorgelig]

576p is a special mode available in workbench only.
Games don't use 480p/586p as they are targeted for TV. So it's either 480i/576i or 240p/288p.
You will have to deal with de-interlacing as it's pretty much used in games.
How it will work when you will lock the resolution and framerate - i don't know. Video chip is pretty much programmable and it's used in games and demos, so it may not work being locked to a single resolution.

[Sorgelig]

I plan to not use any scaler at first, as I seen posts about it causes some flicker on interlaced frames.

And if you look NeoGeo topic you will think the core doesn't work at all
There is no flickers in interlaced modes on HDMI. May be just on moving objects which is unavoidable. Even moving cursor in WB in interlaced mode almost has no flickering.

[kolla]

Even moving cursor in WB in interlaced mode almost has no flickering.

No flickering, but it "tears up" when moving, it gets a "ghost" following it sort of closely

https://youtu.be/E31wCNpdaOs

[Sorgelig]

Even moving cursor in WB in interlaced mode almost has no flickering.

No flickering, but it "tears up" when moving, it gets a "ghost" following it sort of closely

https://youtu.be/E31wCNpdaOs

This is nature of de-interlacing. When object is moving in interlace video, 2 fields are different, so eventually you see the ghosting.
Weaving de-interlace using in Scaler is targeted to static objects which is majority of time. It gives native resolution as sum of 2 fields.
Another "cheap" de-interlacing is BOB which has half resolution with twice higher frame rate. It has bad result for computer graphics with hard color transitions, so it produces a lot of flickering on static objects. So it's definitely not suitable for Minimig. Workbench will be full of flickering lines.
Modern TVs use very sophisticated algos like motion adaptive and others which is not available (it's resource and computing expensive) for MiSTer.

[Sinclair]

The last version of day 12 does not work with 64MB, it comes out red screen. It happens to several users. With 32MB it works fine.

[Sorgelig]

Test version:

Minimig.zip

Some fixes and tweaks for 64MB modules.
It's absolutely required to update MiSTer binary and Menu core which will detect the module size!

[terminator2k2]

that one booted straight away

[Sinclair]

Test version:
Minimig.zip
Some fixes and tweaks for 64MB modules.
It's absolutely required to update MiSTer binary and Menu core which will detect the module size!

Works fine!
Thank you.

[ono]

Does MiSTer Minimig version support writing to ADF disks? Or this is just read-only? Reading upstream Minimig project docs it seems ADF writing is supported.
Btw. This is not a request, just want to confirm there is no ADF write

[R4MS]

Minimig on MiSTer supports reading and writing to 880K ADFs.

[Sinclair]

Test version:
Minimig.zip
Some fixes and tweaks for 64MB modules.
It's absolutely required to update MiSTer binary and Menu core which will detect the module size!

Works fine!
Thank you.

I am sorry to say now that although it boot without problems the system has become unstable with continuous Worbench errors and strange behaviors in some games.

I had to go back to versión 20190717

[Sorgelig]

I am sorry to say now that although it boot without problems the system has become unstable with continuous Worbench errors and strange behaviors in some games.
I have returned agaub to the July version

Are you using official XS version of 64MB module?

[Sinclair]

I am sorry to say now that although it boot without problems the system has become unstable with continuous Worbench errors and strange behaviors in some games.
I have returned agaub to the July version

Are you using official XS version of 64MB module?

Yes, XS 1.1

[Sorgelig]

I am sorry to say now that although it boot without problems the system has become unstable with continuous Worbench errors and strange behaviors in some games.
I have returned agaub to the July version

Are you using official XS version of 64MB module?

Yes, XS 1.1

can you try with 32MB module?

[Sinclair]

Are you using official XS version of 64MB module?

Yes, XS 1.1

can you try with 32MB module?

Yes, works fine.

[Sorgelig]

try this one:

Minimig2.zip

[Sinclair]

try this one:
Minimig2.zip

No, its continue with the same or even more serious errors

[ono]

Minimig on MiSTer supports reading and writing to 880K ADFs.

I think I got bad ADF file. With 880K works great. Thank you!

[petarku]

hi guys , I am connecting mister to 15khz monitor Dell u2410. i am experiencing some slowdowns when playing swos via adf disks which doesnt exist on real amiga.
Does anyone here have the same monitor and what configuration of mister.ini and monitor settings you are using so you will get proper picture?

Best Regards,
Petar