MinimigAGA 1.2: strange dots (graphic issue)

[AmigaIstMiST]

[AmigaIstMiST]

I noticed that there are strange dots on GURUs and on the Kickstart 2.0 start screen. I sadly do not own a real Amiga any more (I sold it and bought a PC for it, I admit it), but I can't remember having seen these dots. When the red guru rectangle is visible, there is also a surplus dot on the left lower side. When the rectangle is not visible, there is a single red dot visible.

[AmigaIstMiST]

Tested this with Kickstart 2.0/3.1 ECS/OCS in NTSC mode. Kickstart 1.x doesn't have this problem. I didnt't verify this with UAE, I will try to do it in a few days and will report the results here.

[AmigaIstMiST]

On UAE Kickstart 2.0 startscreen looks fine, no white dot visible (I didn't check gurus).

[AmigaIstMiST]

https://github.com/rkrajnc/minimig-mist/issues/38

[renaudhelias]

If the dot disappears after unplug/stop plateform during one day long, it's then certainly due to a memory zone not initialized correctly. The dot position seems being at begin of VRAM (it's to say at begin of drawable image on screen), isn't it ?

[AmigaIstMiST]

Hmm, have a look at the 3rd picture, there is a surplus dot under the guru, not on the first position of the drawable area. The behavior is also different between AGA and ECS, like the shifted screen bug.

[renaudhelias]

Some display could start at another offset like in CPC, but begin of RAM (used for video, alias VRAM) is still begin of RAM. The better to do for the author here is to isolate this pixel forcing it on or else off during RAM (VRAM) read to find firstly that there is only one address of the VRAM that is concerned here just before display. This way he could, in a first step, capture this bug.

[renaudhelias]

First test is trying finding someone else having the same problem, isolating in the way all our settings : firmware version, core version.... in a minimal way. Currently I'm not using MinimigAGA, but if you describe me all what I need (could be at renaudhelias@gmail.com or else here ...) I can try to reproduce this bug.

You can also try some more old realises, in case this bug is about regression (something new breaking something old), in this case solution is easy, a classic merge between two versions and then... solved.

A first provocative test could be adding a "NOT" at a high address RAM wire, like this you'll see if it's a RAM quality problem (in this case dot does disappear... this case is not cool : it's a death RAM byte), or else strange dot still appears at the same position, this case is cool : it's a limit of RAM scan area or else a relaxing address position.

It can be also a 100% internal FPGA asynchronous RAM adapter (a RAM with two clocks, one for writing or another for reading, at different speed) currently used for VGA display, in this case testing with an original SCART display shall not display this dot, and correction here shall be changing asynchronous RAM policy, or setting a NOT at enter clock (wr data part) of this asynchronous, a NOT clock build from DCM, respecting like this "timing constraints".

[AmigaIstMiST]

To reproduce the bug:

• use latest firmware, MinimigAGA 1.2.2 beta
• use ECS or OCS chipset
• NTSC or PAL does not matter
• use kickstart 3.1 for Amiga 500 (!)
• guru somehow :-) The dot appears in VGA and in SCART configuration.

The dot does not appear, if I use kickstart 1.x (strange, isn't it?) and ECS/OCS. The dot also does not appear, if i use the AGA chipset and kickstart 3.1 for Amiga 1200.

I don't think that there is something wrong with my MiST hardware. My idea was, that it is related to the "shifted screen" bug, because of the different behavior between AGA and OCS/ECS. But it is also very strange, that the behavior is different between different kickstart version using ECS chipset.

[renaudhelias]

a beta version is a version not finalized yet (but that does something cool), I think it's the way to go.

[renaudhelias]

https://github.com/rkrajnc/minimig-mist/issues/44

[AmigaIstMiST]

The dot also appears in 1.2, it was not introduced in the beta version.

[AmigaIstMiST]

Fixed in V 1.2.3