From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: RTG? And Graphics Cards???
Date: 11 Dec 92 12:49:25 GMT
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA

In article <ByAoqA.9DB@cs.columbia.edu> won@cs.columbia.edu (Won Y. Kim) writes:
>In article <1992Nov25.215607.7108@jato.jpl.nasa.gov> jdickson@jato.jpl.nasa.gov (Jeff Dickson) writes:
>>In article <92330.162444K3023E2@ALIJKU11.BITNET> <K3023E2@ALIJKU11.BITNET> writes:
>>>Could someone post here what these two Labels mean? I couldn't find it
>>>out til now.
>>DIG I know (Device Independant Graphics), but RTG escapes me (RadioIsotope
>>Thermal Generator?).

>ReTargetable Graphics. Superset of DIG

RTG does stand for Retargetable Graphics, but RTG isn't a superset of DIG.
Basically, there are various tiers of graphics support a system can provide.
It might look something like this:

	HW Registers			VGA under MS-DOS

	Dedicated Hardware Class	Amiga Graphics.Library (today)

	Generic Hardware Class		Macintosh QuickDraw

	RTG				X-Windows

	DIG				Display Postscript

Basically, IBM simply gave you hardware.  Anyone who wanted to write a program
banged on the CGA->VGA->Whatever registers, which became documented.  As in all
graphics systems, this was a combination of hardware and software, only the
software element was basically nonexistant (the PC BIOS could do some small
things independently of display device, like text).

The Amiga OS currently supports a range of different but similar graphics 
chips.  As long as you stick to the programming interface, you will work with 
the future RTG system.  But for now, things are mainly stuck on the Amiga
hardware (things is already going away, as folks are writing "Intuition
Drivers" for foreign display boards.  I got one called oMniBus in Germany
that puts Amiga displays up on a TSENG VGA card.  Pretty decent).

The Mac OS currently supports any graphics board that is basically a naturally
mapped chunky pixel display in one of several resolutions.  This isn't quite
RTG, but since the specs for this were in place before any foreign hardware
existed, everything you hook up to a Mac conforms.  The only downside is that
the Mac's graphics system can't take much advantage of graphics processors
(though it does get some mileage out of general purpose processors, so you see
AMD 29Ks or ARM chips rather than TIGA on the Mac).

RTG basically defines a system that lets the same software interface drive
any kind of hardware.  I think X is the best example of this, since the driving
program and the display are commonly separated by a network, which requires
true device isolation.

DIG is a superset of RTG.  The device isolation of an RTG system is 
bidirectional -- function calls do the actual work of generating a display,
but the driving program needs to know something about the physical geometry
of the display device to create a proper display.  DIG can be one-directional
(the imaging model, though of course a DIG-based GUI will have two-way
communication outside of the imaging model).  DPS is a good example.  Anyone
who's used PostScript knows that it's necessarily one direction -- I always
dump PostScript to a file and copy it over the network here to our laser
printer.  The program that generates the DIG image description doesn't have
to interact at all with the program that knows about the underlying hardware
of the imaging device.

>3. descent speed. (faster than A2410 puh-leez!)

You'll probably need a Zorro III card for this.  If there are 34020 based
cards for Zorro II, they're likely faster than the A2024.  Other accelerated
cards may also be faster to some extent, but the bottleneck will ultimately
be the bus.  AmeriStar makes a dandy Zorro III display board called the
1600GX.  It uses a Weitek blit chip (I think they use these in SparcStations)
and can handle 1600x1200x8 noninterlaced.  It looked pretty fast to me
under AmigaUNIX, though I didn't have enough time to get a real good feel.
In any case, this one isn't cheap.  But if you want beyond typical SVGA
(1024x768ni/1280x1024i), you have to pay for it.  The monitor will likely be
the real expense.

>4. the last and most importantly, DEVELOPER'S KIT for BOTH AmigaDOS and
>AmigaUNIX!! (VERY IMNPORTANT!!!!)

I don't know what solution they offer for AmigaOS.  These "Intuition
Drivers" are becoming increasingly common.  I ran into all kinds of boards
running Workbench while at the World of Commodore show in Frankfurt.  This
"oMniBus" card I came back with was one.  This is actually just a bus
converting bridgecard kind of thing with a programmable video switch.
The software drives a VGA card over the Zorro II bus, and it's reasonably
smart about getting out of the way for Amiga screens (thus the switch).  
They're still perfecting the software, but it's already stable enough to 
program under (though I now need a new monitor, the 1950 just doesn't cut
it, it barely handles 800x600).

>(no humoungous fee for the dev's kit, if at all possible, unlike for the 
>A2410, which irked me a BIT)

I think that was due to TI and the TIGA library, nothing under control of
Commodore or ULowell.

-- 
Dave Haynie / Commodore Technology, High-End Amiga Systems Design (cool stuff)
 "The Crew That Never Rests"  {uunet|pyramid|rutgers}!cbmvax!daveh   BIX: hazy
		SCIENCE:	"I'll believe it when I see it"  
		RELIGION:	"I'll see it when I believe it"