Amiga AGA RTG

[Karlos]

ReTargettable Graphics

The idea behind RTG is that an application doesnt't need to know exactly what hardware is powering the display.

Just to  muddy the issue, stuff written specifically for AGA will usually outperform RTG stuff that happens to work on AGA.  Additionally a lot of RTG stuff exists that assumes you have a graphics card and won't work on AGA only systems.

[Karlos]

An FPU will speed up only a specific subset of operations involving floating point arithmetic. And then it will only do it if the software was compiled for it. Stuff like rendering etc are the biggest users of FPU. Software compiled to use the mathiee#? libaries will be accelerated if you get appropriate replacement libraries.

Stuff like graphical operations and archiving are typically integer operation based and hence unaffected by the presence of an FPU.

The only graphical systems assisted by FPU are things like Warp3D/OpenGL which need much higher spec systems to start with.

[Karlos]

One thing to be aware of with respect to RTG, assuming you are performance obsessed like yours truly, at least on classic systems, is that they tend to massively underutilize the GPU for rendering tasks.

Most stuff ends up being rendered by software under Picasso96 / CGX on the vast majority of graphics cards, even when the card supports a full range of 2D operations directly. I did a *lot* of experimentation in this area up to about a year ago. Often only basic blits between identical BitMap formats, rectangle fills and sometimes line drawing are accelerated by RTG. Transparent blits, scaled blits, pixel converting blits (from one format to another) polygon fills etc tend to be entirely CPU driven regardless if the GPU offers these operations. Which I find immensely irritating ;-)

The speed up a graphics card gives you is principally down to the fact that you have a faster bus on which to shovel pixel data to the video memory ;-0

[Karlos]

itix wrote:

An FPU will speed up only a specific subset of operations involving floating point arithmetic. And then it will only do it if the software was compiled for it. Stuff like rendering etc are the biggest users of FPU. Software compiled to use the mathiee#? libaries will be accelerated if you get appropriate replacement libraries.

But for example FPU version of mpega.library is slower than integer version without FPU. However FPU version provides better quality of output.

True, but this is a very specific example. Arguably you could still say it is faster - the integer version to attain a comparable quality would likely be slower.