1024x768 31khz AGA.. is it possible???

[AmiBiL0]

Hello everyone.
I am trying to increase the size of the screen.
I would love to have a 1024x768 if I could but the only monitor driver
or hacks are 21 khz and they don`t work on my monitor or my doubler.
the scan doubler only accept the 15 reguralr frequency and the monitor only 31.

Some monitor have the size that I want but the view size is always smaller and I can`t find a way to change it.

Any ideas anyone?

PS: I`m trying to do this on a A1200.
Please any suggestion welcome

BiL0

[SamOS39]

I dont think its possible, youll need a graphiccs card.

It couldnt handle that screen res becuase the GPU probly isnt powerfull enough and theres only 2MB video ram.

correct me if im wrong ..  :-)

[motorollin]

I don't think it's possible. I think this is how it works:

1024x768x8 = 6,291,456

So there would not be enough chip memory to display even an 8 bit screenmode.

--
moto

[Doppie1200]

Also the chipset is not fast enough to fetch the 1024 witnin the time it takes to draw the scanline in case of 31khz. Ofcouse you can get 1280x512 at 15khz

1024x768 VGA was really only fot very high end in 1992. The Amiga certainly wasn't with its chipset

[AmiBiL0]

wich monitor driver should I use to get the 1280x512? at 15?

anyway there is a hack and a new monitor driver for the AGA at 1024x768 but it only works at 21 which is a strange frequency and unless you have a multisynk monitor then you can't really use it.

what I am after is any resolution that it is bigger then 640x480 (the one I am using at the moment.. 31 would be preferible but 15 will do as well

thanx in advance

BiL0

[Zac67]

@moto:

This is bits you're talking, that's only 768 KByte. ;-)

[pVC]

AmiBiL0: 1280 x 512 @ 15kHz is just standard AGA resolution (in PAL driver), superhires laced mode.

At AGA times I used 800x600 with Super72 driver I think... hmm.. but it was only 23kHz or something.

[AmiBiL0]

I tried lots of (if not all) the monitor drivers and on everyone of them you have a larger resolution, but the view size you can't really change. so the scree will go from one side to the other when you move the mouse but that's not what I am after.
I just need a bigger resolution so that the space on the Workbench looks bigger. is DblPall better? I haven't tried that one yet.

PS: I have a 1230 with 32 MB on it. would that make any difference? maybe not as the chip memory is still 2MB

Thanx to all anyway

BiL0

[pVC]

AmiBiL0: Umm.. every mode should change the visible resolution of the screen. Virtual sizes are different and they're purely what you set to them. Do you have "default" option for size checked in screenmode prefs?

[zipper]

The only solution I know is Highgfx from Aminet, which offers 1024x768 interlaced mode for AGA/ECS. Never tried, it must be slow and no idea what the frequencies are.

[Ilwrath]

As I understand how things work...  (And my understanding is limited to inventing a few custom original arcade screenmodes for MAME on CyberGraphX)

1024x768x31000(31KHz) = 24.38MHz
This is the required pixel clock.

Hmm...  As best as I can tell, the maximum AGA pixel clock is 28mhz.  28 > 24, so theoretically, this mode might be possible.  I have no idea how much (if anything) is lost to overhead.  All I really know is that I've never seen a driver do it.  If you manage to get it to work, let us know!


[EDIT: You may want to highly disregard the calculations above -- I think I did something very wrong.  I don't think it's that simple a calculation.]

[Ilwrath]

Alright.  Upon review, I really screwed this up.

I consulted with some X Screenmode Definition tutorials, and I'm ready for round 2.

Here's something closer to the truth:

1024x768.  First, you need to take into account overhead for the sync...
htotal ~= width*1.2
vtotal ~= height*1.1

So....
for total, we're looking at ~1230x850

now, for 31KHz horiz sync (31x1230), we need a minimum of a 38MHz pixel clock.  Well out of range of AGA.  Not gonna happen.

The driver that gave a 21KHz horiz sync (21x1230), would need a minimum of a 25.8mhz pixel clock.  Right at the ragged edge of the max value I found for AGA (28mhz).  I bet that's why it used such an odd value.

[Marco]

So what's the highest normal aspect res that can produce 31kHz output within the bounds of AGA? Although I'm assuming that whatever it is wouldn't be worth it as you'd have a silly colour depth beyond the 640x256 high-res anyway

[Kronos]

@Marco

AGA can do 256 colors right upto 1280x256 (+ overscan), whic is the base for all the Multiscan, Euro72,DbPal, Super72, etc modes.

Don't know whats really done on the modes that go beyond that.

[DamageX]

The pixel clock is number of pixels (horizontal resolution + horizontal retrace) * number of lines (displayed lines + vertical retrace) * refresh rate. For example, NTSC low res is: (320+135)*(200+62)*60=7.16MHz
The Amiga has three possibilities low res, high res, super-high res (28.6MHz NTSC, 28.3MHz PAL)

720x480x60hz or 720x512x50hz plus a bit of overscan is about as good as it gets without interlacing. As previously mentioned, you can get 800x600x70hz interlaced on a 24KHz monitor and the flicker probably isn't too bad (at least compared to a 15KHz monitor).

Since AGA can do 8 bitplanes in super-high res (with 64-bit aligned fetches) it can do it in any possible resolution, but CPU-chipmem bandwidth gets progressively slower going beyond 4 bitplanes in super-high res