Thread: Graffiti card
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Old 29 October 2012, 00:02   #19
NovaCoder
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Join Date: Sep 2007
Location: Melbourne/Australia
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I'm not an expert in how Graffiti works but this is what I've read so far:

1) ECS Graffiti is pointless (note that the recent IndivisionECS Direct frame buffer updates to ADoom (v1.4) is not using Graffiti).
2) The main benefit of Graffiti seems to be that it uses less data to display an 8bit image vs planar AGA (this is important because the CHIPRAM writes across the bus are very slow in Amiga town).

According to the docs on Jen's site, it appears that you don't need to perform C2P when using Graffiti.

Quote:
Originally Posted by Jens
Graffiti changes the Amiga bitplaned graphics into a chunky
pixel mode. I.e. one byte in memory represents a single
pixel. The value of a byte selects it's colour. The colour
palette is 256 out of 262144 at a time. Possible
resolutions are 640x256, 320x256, 160x256 and 80x256. In
each mode, 256 colours are available, interlacing doubles
the vertical resolution.

For full speed advantages, AGA Chipset or the A3000 are
recommended. For more speed, accelerator cards with
burstmode fastmem are recommended.

Due to the limited bandwidth of the chipmemory, the frame
rate of a motion sequence is limited. At about 7MB/s on
AGA-chipsets using 4 Bpls hires, with longword-access about
74 frames/s can be transferred - more than required.
Graffiti

BTW, Jens has confirmed the Indy Mrk2 will support an extended Graffiti mode that will support a 24bit palette (currently only an 18bit palette is supported).

Last edited by NovaCoder; 29 October 2012 at 00:33.
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