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AuthorTopic: ScanPlus AGA issue  (Read 382 times)

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Offline bradhansen1

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ScanPlus AGA issue
« on: June 18, 2022, 12:54:52 AM »
Hi All, I have installed a ScanPlus AGA in my A1200. I'm running OS3.2.1,
I want to run this on a VGA BENQ flat panel in DBLNTSC HiRes No Flicker.
What I have discovered is that the system will not boot up straight into
this mode. And I must go to the boot screen and and then hit "Return" to
switch to 31kHz and then boot. Question? Is there a setup where I can just
boot into the mode or must I do this everytime?
Appreciate any help.
Brad Hansen
 

Offline Matt_H

Re: ScanPlus AGA issue
« Reply #1 on: June 18, 2022, 01:51:59 AM »
I'm not quite sure I understand your question. If you have a scandoubler, there's no need to force the system to use "native" 31KHz modes. The purpose of DblNTSC is to get NTSC resolutions on non-NTSC monitors (i.e., 31KHz VGA monitors), but it's much more strenuous on the chipset and therefore considerably slower.

The scandoubler offloads all that work for you. With a scandoubler, NTSC HiRes Laced will give you the exact same resolution/functionality as DblNTSC HiRes NoFlicker but it will be much faster.

Other notes:
By "boot screen" I guess you mean the Early Startup Control menu (from holding both mouse buttons at boot)? That will always be plain NTSC (or PAL) until forced into another mode with a keyboard override. I'm not certain of this, but there might be ROM modules that can change it without an override, but those will first need to be kicked in as part of the startup-sequence or added to a custom-burned ROM. But again, none of this should matter if you have a scandoubler.

Maybe you know this already, but to permanently set your Workbench screenmode, the appropriate Monitor file needs to be in SYS:Devs/Monitors, which will enable it during bootup. To then switch to one of those modes, use SYS:Prefs/Screenmode. Select a mode and hit Save. It's a good idea to test the mode first to ensure the display can handle it.
« Last Edit: June 18, 2022, 01:52:41 AM by Matt_H »
 

Offline bradhansen1

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Re: ScanPlus AGA issue
« Reply #2 on: June 18, 2022, 08:07:02 PM »
Matt, been an Amiga owner since 1988. I don’t know if it’s a hang up of OS3.2.1, but I can not just set my screen
mode to DBLNTSC and have it start up in that mode. my BENQ monitor says”Out of range. It’s only when I switch to
31kHz in the boot screen that it will startup in DBLNTSC. That is how it’s working on the ScanPlus AGA anyway. I have a
TF1230 accelerator and have not noticed any slow down when working in DBLNTSC, which where I want to be.
 

Offline Matt_H

Re: ScanPlus AGA issue
« Reply #3 on: June 18, 2022, 08:44:09 PM »
Ok, I think I have a better idea of your question now. I don't know the nuances of your particular scandoubler, but I know some of them will simply pass-through pre-doubled modes like DblNTSC. I wonder if that's what's happening. The reason that could present an issue is because DblNTSC isn't *quite* a 31KHz mode, so maybe the Benq can't handle it. If you put VGAOnly in Devs:Monitors that might clear it up. VGAOnly tweaks those almost-VGA screenmodes to make them fully VGA-compliant. There is some sort of drawback, but I don't remember what it is and it's very minor. I wonder if manually overriding the Early Startup Control menu to 31KHz is performing a similar sort of effect.

Does the ScanPlus itself have any sort of config options? That might be worth looking at, too.

The speed penalty of DblNTSC probably won't be very noticeable with 4- or 16-color screens, but once you start getting into 256-color screens and using DblNTSC for 3D games you're going to see a performance hit compared to plain NTSC - it's pushing twice the amount of data through the chipset.

(And I know you've been a user for a long time but I thought I remembered a lot of your previous posts having to do with 1.3, so I thought you might be new-ish to OS3 ;) )
 

Offline bradhansen1

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Re: ScanPlus AGA issue
« Reply #4 on: June 19, 2022, 11:27:50 PM »
Matt, Thanks for staying on this for me. Your right DBLNTSC is 29.9kHz so that may be why. The ScanPlus
is just plug and play, no preferences or options. I have a raspberry pi 3+ and have setup 5 Amiga systems on
it starting with a 1.3 A500. I’ll stick the VGA Only in there and see what happens. Thanks again.
 

Offline bradhansen1

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Re: ScanPlus AGA issue
« Reply #5 on: June 20, 2022, 07:50:58 PM »
Hi Matt, That worked! Boots up into DBLNTSC no problem, thanks!
 

Offline Matt_H

Re: ScanPlus AGA issue
« Reply #6 on: June 20, 2022, 08:55:46 PM »
Great! Glad that worked.

I am curious about the internal mechanics of how the Early Startup override worked since that’s all ROM code… but that’s a technical discussion for another time. ;)