update from s-media regarding landscape flicker

[joerg]

Am Di  25. März 2008 schrieb Andy Green:
> - gpg control packet
> Somebody in the thread at some point said:
> 
> > **pixelclock** has to go down in landscape? Is this for the different 
address
> > sequence scheme in RAM for each of the 2 modes, or does glamo some 
internal
> > transformation by blitting, thus eating 2/3 of the bandwidth or what?
> 
> Yes, I guess the problem for this chip comes from the fact it still
> issues a portrait raster to the LCM, so it has to compose each portrait
> line from pixels that are totally disjoint in memory.
> 
> In portrait, adjacent pixels are in ascending order in memory, so after
> issuing the address to the DRAM and paying the penalty for random
> access, prefetch or block fetch modes from the memory work well since
> you are going to use that data for the next pixels.

Really bad: if data in video memory is 15bit-packed, and thus not word aligned 
(hypothetically! i don't believe in this), glamo has to fetch 15bytes per 16 
pixel in portrait, and 31bytes per 16 pixel in landscape. :-/

jOERG