1024x768 x 24 not possible on Cybervision64 ?!

[patrik]

@Jose:

The reason for this is as I wrote in the earlier thread Amigaz linked to, is that the maximum pixelclock decreases drasticly with increased depth of the resolutions. This simply because the bandwidth between the Trio64 chip and the onboard VRAM is not enough for more. This what is supposed to be max pixelclock for each bit-depth:

8-bit - 130MHz max
16-bit - 80MHz max
24-bit - 50MHz max

I have though experienced that if you use a higher pixelclock than ~48MHz in 24-bit, there will be graphics corruption, especially when stuff is moving on the screen.


/Patrik

[patrik]

@AMIGAZ:

To get a 16-bit screenmode in 1024x768:

Start CGXMode and select a monitor corresponding to the limitations of yours. If you can find your monitor in the list - select that one, else select "Monitor-85kHz" - that one will allow you to drive the CV64 to the limit, which your 17" Trinitron will have no problems handling.

When that is done, create a new screenmode, select 16-bit as type and then select "1024x768 (75Hz, 60kHz) VESA" from the list of predefined screenmodes and press "Ok". Then save, reboot and voila - you have a 1024x768 screenmode in 16-bit.


/Patrik

[patrik]

@AMIGAZ:

Dude, my thoughts are with you.. creating screenmodes with Picasso96Mode is lethal .


/Patrik

[patrik]

@zipper:

Yeah, you are right - it's 135MHz at 8-bit. Sounds reasonable as that is what is required for a 1280x1024 VESA speced screenmode at 75Hz.

At 16-bit though, I am certain the max is 80MHz, unless you remove the limits in CGXMode (cant remember the tooltype for that), which will allow to go to 110MHz or something I think, but using a higher pixelclock than 80MHz will drop the cards performance quickly as it will start to cut significantly from the bandwidth supposed to be over for the Trio64 chip and Amiga cpu to draw into the vram.

Btw, 80MHz is just above whats required for a 1024x768 VESA speced screenmode at 75Hz, so it is a reasonable limit.


/Patrik