TT Software overscan?

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Cyprian
Posts: 59
Joined: Fri Dec 22, 2017 9:16 am

Re: TT Software overscan?

Post by Cyprian » Sun Jun 17, 2018 7:10 pm

arf wrote:
Thu Jun 07, 2018 10:25 pm
Do you mind sharing the name and/or download link of the software?
DBL2STE.PRG for STE and DBL2ST.PRG for ST

it uses interlace effect to boost ST wideo modes: ST-LOW into 320x400i in 16 and ST-MID 640x400i in 4 colors
Jaugar / TT030 / Mega STe / 800 XL / 1040 STe / Falcon030 / 65 XE / 520 STm / SM124 / SC1435
SDrive / PAK68/3 / CosmosEx / SatanDisk / UltraSatan / USB Floppy Drive Emulator / Eiffel / SIO2PC / Crazy Dots / PAM Net
Hatari / Steem SSE / Aranym / Saint
http://260ste.appspot.com/

atari030
Posts: 50
Joined: Mon Feb 12, 2018 12:43 pm

Re: TT Software overscan?

Post by atari030 » Mon Jun 18, 2018 10:56 am

That's the one. Didn't realise there was an ST version.

Cyprian
Posts: 59
Joined: Fri Dec 22, 2017 9:16 am

Re: TT Software overscan?

Post by Cyprian » Mon Jun 18, 2018 12:20 pm

Petari wrote:
Thu Jun 07, 2018 7:59 pm
On ST(E) overscan is achieved by making some writes to video registers (for freq. change) in very accurate moments of horizontal scanline. That's possible only with 100% CPU load, and knowing exact instruction execution times (cycle count) . Luckily, you can use there not only delays, but something like palette change - of course, with rigid execution time. I know only one SW, what does something else - Overscan Invaders. But that game is easy for ST, so was possible to make such code what moves objects and other, while cycle count is same. There is however one issue - it works only with keyboard. I tried to add joystick input, but that screwed timing (not because added cycles - I subtracted what it added, but because not same cycle count every time), and then graphic went corrupted. Could not solve it in simple way, so abandoned.

On TT must be same principle - and that means that CPU speed helps not - timing is what is problem. And you can not use some other way, because it will be not cycle accurate. Some will say: use Timer-B - but that's not good enough, because interrupt of it will not happen cycle accurate - it depends from what instruction executes in moment of interrupt. No wonder that it works only as slide show on TT too.
Just get some VME graphic card :lol:

sometimes ago I did some tests and a classic ST sync-code works fine on the TT:

Code: Select all

    lea    $ffff8209.w,a1

sync
    move.b    (a1),d0
    beq.b    sync
    not.b    d0
    lsl.b    d0,d0
Thanks to that, we can get stable raster on the TT.
Therefore there is a chance that software overscan could be reached.
Jaugar / TT030 / Mega STe / 800 XL / 1040 STe / Falcon030 / 65 XE / 520 STm / SM124 / SC1435
SDrive / PAK68/3 / CosmosEx / SatanDisk / UltraSatan / USB Floppy Drive Emulator / Eiffel / SIO2PC / Crazy Dots / PAM Net
Hatari / Steem SSE / Aranym / Saint
http://260ste.appspot.com/

Petari
Posts: 528
Joined: Tue Nov 28, 2017 1:32 pm

Re: TT Software overscan?

Post by Petari » Mon Jun 18, 2018 12:44 pm

Cyprian wrote:
Mon Jun 18, 2018 12:20 pm

sometimes ago I did some tests and a classic ST sync-code works fine on the TT:

Code: Select all

    lea    $ffff8209.w,a1

sync
    move.b    (a1),d0
    beq.b    sync
    not.b    d0
    lsl.b    d0,d0
Thanks to that, we can get stable raster on the TT.
Therefore there is a chance that software overscan could be reached.
It is not dilemma here that SW overscan is possible on TT. It is just that it occupies CPU in way, that can not run SW then normally .
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

Cyprian
Posts: 59
Joined: Fri Dec 22, 2017 9:16 am

Re: TT Software overscan?

Post by Cyprian » Mon Jun 18, 2018 1:30 pm

Petari wrote:
Mon Jun 18, 2018 12:44 pm
It is not dilemma here that SW overscan is possible on TT. It is just that it occupies CPU in way, that can not run SW then normally .
true.
Jaugar / TT030 / Mega STe / 800 XL / 1040 STe / Falcon030 / 65 XE / 520 STm / SM124 / SC1435
SDrive / PAK68/3 / CosmosEx / SatanDisk / UltraSatan / USB Floppy Drive Emulator / Eiffel / SIO2PC / Crazy Dots / PAM Net
Hatari / Steem SSE / Aranym / Saint
http://260ste.appspot.com/

mrbombermillzy
Posts: 51
Joined: Sun Jun 03, 2018 7:37 pm

Re: TT Software overscan?

Post by mrbombermillzy » Mon Jun 18, 2018 10:01 pm

Cyprian wrote:
Mon Jun 18, 2018 12:20 pm

sometimes ago I did some tests and a classic ST sync-code works fine on the TT:

Code: Select all

    lea    $ffff8209.w,a1

sync
    move.b    (a1),d0
    beq.b    sync
    not.b    d0
    lsl.b    d0,d0
Thanks to that, we can get stable raster on the TT.
Therefore there is a chance that software overscan could be reached.
Interesting work there Cyprian... One day when I get to my TT again I will have to pick your brains! :D

Im still intrigued with what Ray did for the 1280x480i slideshow demo, as according to the HW TT overscan manual linked earlier by Frank Lucas, TT Med Res is only 832px wide. He has somehow traded vertical resolution for either a 1: LOWERING of H.Freq or 2: a higher dotclk?? I have managed such things on a more programmable Commodore video chip, but I didnt think the TT shifter was this flexible.

Cyprian
Posts: 59
Joined: Fri Dec 22, 2017 9:16 am

Re: TT Software overscan?

Post by Cyprian » Thu Jun 21, 2018 11:57 pm

mrbombermillzy wrote:
Mon Jun 18, 2018 10:01 pm
Interesting work there Cyprian... One day when I get to my TT again I will have to pick your brains! :D
:)
mrbombermillzy wrote:
Mon Jun 18, 2018 10:01 pm
Im still intrigued with what Ray did for the 1280x480i slideshow demo, as according to the HW TT overscan manual linked earlier by Frank Lucas, TT Med Res is only 832px wide. He has somehow traded vertical resolution for either a 1: LOWERING of H.Freq or 2: a higher dotclk?? I have managed such things on a more programmable Commodore video chip, but I didnt think the TT shifter was this flexible.
Actually, IIRC this is a simple trick - it just shows very quickly two images alternately. Both are 640x480 16colors.
Jaugar / TT030 / Mega STe / 800 XL / 1040 STe / Falcon030 / 65 XE / 520 STm / SM124 / SC1435
SDrive / PAK68/3 / CosmosEx / SatanDisk / UltraSatan / USB Floppy Drive Emulator / Eiffel / SIO2PC / Crazy Dots / PAM Net
Hatari / Steem SSE / Aranym / Saint
http://260ste.appspot.com/

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