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Documentation about the Vampire hardware

Saga Pixel Speed?

Andy Hearn

Posts 374
30 Jan 2018 12:59


Hi all,
Sorry if this has been answered already, and I'm sure it has, but i'm just trying to look up the max pixel speed of the Saga Picasso driver?
IIRC, people can get:-
1920x1080@24bpp@24hz = ~142MB/s
and
1280x720@24bpp@60hz = ~160MB/s

which on DIGITAL-VIDEO v1.0 gives me a rough pixel speed for the bandwidth needed of 55Mhz at 8/10b encoding

i'm at work, not at home, hence the back-of-an-envelope excel sheet, and that I can't just fire up a vampire to see

reason i'm asking is I've unearthed some matrox-triple-head-2-go boxes and wondering if I can get enough data into it to drive 2 or 3 screens...
3x 640x480@24bpp@60hz looks like its going to be about 160MB/s
2x 800x600@24bpp@60hz looks to be around 110MB/s

I remember trying this over the VGA out from my Blizzard vision. it kinda worked, but it seemed that you only had a small window of flexibility to get the timings right for the analogue signal, so a lot of faffing about plus the hardware limit of a 2000pixel bitmap from the permedia2 chip just killed my limited patience :D

hoping that using the digital output leads to an easier setup experience.


Gunnar von Boehn
(Apollo Team Member)
Posts 6207
30 Jan 2018 13:10


Some GFX information about VAMPIRE 2
 
640x480@60 ~ 25 MHz Pixel Clock
800x600@60 ~ 40 MHz Pixel Clock
960x540@50/60 ~ 40 MHz Pixel Clock  ** This resolution is our recommendation **
 
Depending on your TV you can also try:
1280x720@30 ~ 33 MHz Pixel Clock
1280x720@60 ~ 65 MHz Pixel Clock  ** on the Edge **
1920x1080@24 ~ 65 MHz Pixel Clock ** on the Edge **


Andy Hearn

Posts 374
30 Jan 2018 13:16


perfect! many thanks for the fast reply! :D

hmmm, ok, so on a 65Mhz pixel clock, we're looking at about a max of ~180Mb/s, that may give me enough headroom for 3x 800x600@16bpp@60hz

but again, is this something that's going to be usable, or just an academic exercise... :D


Gunnar von Boehn
(Apollo Team Member)
Posts 6207
30 Jan 2018 13:49


Andy Hearn wrote:

  perfect! many thanks for the fast reply! :D
 
  hmmm, ok, so on a 65Mhz pixel clock, we're looking at about a max of ~180Mb/s, that may give me enough headroom for 3x 800x600@16bpp@60hz
 

 
Not sure what you going to try.
For Display you have to consider 2 values: Pixelclock and Bandwidth.
Pixelclock is the Number of pixels that you transfer over the cable.
This number includes visible and invisible pixel (in borders)

Bandwidth is the number of visible pixel x bitdepth of the screenmode. Bandwidth increase with more colors.
But Pixelclock does stay constant.

So a Screen with the same resolution but 24bit color and 2 colors will have the same Pixelclock.

 


Mallagan Bellator

Posts 393
30 Jan 2018 17:52


I think what he means to try is splitting the screen onto 3 different monitors using a split box, or what they are called.
Hdmi connector from vamp goes into the box, that in turn splits the image up over 3 other monitor outputs


Andy Hearn

Posts 374
31 Jan 2018 13:54


yup. it is it's own little frame buffer. with both VGA and DVI in.
  it'll present itself downstream dependent as to what screens it has attached and their capabilities.
  so if it has two 19" lcd's that can each display 1280x1024, it'll say to anything connected on the input side, "hey, i'm a monitor that has a max res of 2560x1024". so for example, 3x 640x480 screens need the source to "just" generate a 1920x480 screen - in theory...
 
  The permedia2 max bitmap size was 2000 pixels, and I just couldn't get the timings right over the VGA port to push that many pixels without "unsupported signal sync" or some such error.
 
  The indivisionAGA has digital output - a good start, but I just couldn't get enough data out relying on the base AGA timings. maybe if i'd gotten the picasso96 Indivision drivers sorted out....
 
  it did amuse me that the splitter box was happy enough to show the guru meditation screen over three monitors though...

posts 6