Amiga AGA RTG

[cynkronyze]

Hi guys,

can any of you explain what does RTG stand for?

I know that AGA is advanced graphics architecture.

AGA games are good

AGA RTG are amazing......so wahts the difference?

thanks

[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.

[Thomas]

RTG stands for ReTargetable Graphics and is a standard phrase for graphics card drivers. OCS/ECS/AGA are natively supported by AmigaOS, but AmigaOS is not ready for RTG. So graphics card drivers need to hack into the OS in order to work. That's why there is such a strict differentiation between native and RTG screen modes when regarding the Amiga.

Bye,
Thomas

[alexatkin]

Sorry to takeover the thread, although I think the question has been answered sufficiently to be safe.

So, you can support RTG with standard AGA hardware?

If I understand that right its because one of the major limitations with AGA games is they were designed for stock A1200 with 2MB CHIP RAM for EVERYTHING. Whereas RTG stuff will vary as its NOT for stock hardware so will use higher colour modes.  And as more CHIP RAM will be available you CAN use higher colour modes than stock AGA games could have.

If all the above is true, is there a guide to installing Workbench on Amigas with accelerators and how customised would you recommend for a stock AGA system running a 50Mhz 030?  Will it be worth getting an FPU?  I understand that an FPU can take HUGE burdon off the CPU and does number crunching a lot faster too for things like archivers, but will it be any major benefit such as speeding up graphics operations?  The more I can push out of the AGA chipset the better, in fact thats part of the challenge. To see how much I can get out of the A1200 without spending stupid amounts of money that would be better spent on upgrading my PC.

And to get back on topic.  I presume that RTG is very similar (although on a more basic level I expect) to Direct X in that respect.  Its a middleware API so you only have to speak one language and RTG handles translating into something the graphics card understands, right?

[itix]

FPU doesnt speed up Amiga at all.

[Piru]

@alexatkin

If I understand that right its because one of the major limitations with AGA games is they were designed for stock A1200 with 2MB CHIP RAM for EVERYTHING. Whereas RTG stuff will vary as its NOT for stock hardware so will use higher colour modes. And as more CHIP RAM will be available you CAN use higher colour modes than stock AGA games could have.

Well, the graphics memory with the gfxcard has nothing to do with "chip memory", but other that that, yes that's pretty much it. Also, the graphics cards typically can generate higher frequency & resolution displays due to faster memory and chipset. Most gfxcards have at least 2MB graphics memory, typically 4/8MB or more (naturally this depends on the gfxcard in question).

Gfxcards (with fast bus) are much faster for things that need chunky graphics, there is no need for chunky2planar conversion.

Will it be worth getting an FPU?

Depends on if you have applications that benefit from FPU. Normally FPU is not needed.

I understand that an FPU can take HUGE burdon off the CPU

Not really, FPU needs special support from the software. But if application supports FPU it can potentially be couple of times faster than integer math version.

and does number crunching a lot faster too for things like archivers

No.

but will it be any major benefit such as speeding up graphics operations?

No.

And to get back on topic. I presume that RTG is very similar (although on a more basic level I expect) to Direct X in that respect. Its a middleware API so you only have to speak one language and RTG handles translating into something the graphics card understands, right?

Correct (to some extent). DirectX does much much more than amiga RTG. RTG patches to regular graphics.library, layers.library and intuition.library, providing OS friendly apps way to access the graphics card hardware. Truecolor routines are available thru additional API (Picasso96API.library for Picasso96, cybergraphics.library for CyberGraphX and Picasso96). RTG itself has drivers for various graphics cards.

[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.

[itix]

I presume that RTG is very similar (although on a more basic level I expect) to Direct X in that respect.

Not at all. Direct X is low level API for games. RTG is more like a driver system for graphics cards and replaces original rendering routines by its own driver system.

[itix]

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.

[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.

[alexatkin]

When I was referring to chip RAM it was because I was trying to find out what AGA RTG was.  If its RTG but sat on top of normal AGA chipset then surely it IS related to chip RAM as that IS one and the same as graphics RAM. The higher the bitdepth the more of that 2MB it will use up. Therefore if you have FAST RAM it follows that you can use a higher bit depth because more graphics memory is available due to most of the stuff that previously was in graphics memory is now in FAST RAM instead.

[Flashlab]

If I recall correctly there's a AGA RTG driver for CGX. That's the closest you'll get to AGA RTG I guess.

[zipper]

But just for CGX v.3

[itix]

The higher the bitdepth the more of that 2MB it will use up. Therefore if you have FAST RAM it follows that you can use a higher bit depth because more graphics memory is available due to most of the stuff that previously was in graphics memory is now in FAST RAM instead.

AGA still couldnt use more than 8 bit planes at once. But AGA could be wrapped inside RTG where offscreen bitmaps were allocated from fast ram and chip ram was reserved for screens. Unfortunately manipulating planar bitmaps by CPU is insanely slow, 8bit AGA screens are insanely slow, not to mention insanely slow chip ram bus.