This review of the AGA chipset was published in the magazine Just Amiga Monthly in the end of 1992, it was written by Jolyon Ralph.

Advanced Graphics Architecture, Workbench 2.1, Kickstart 3.0 and other new things

The new Amiga chipset is finally here! After years of development by Commodore, the Amiga 4000, announced at the World of Commodore show

As a developer, I have known most of the information about the Advanced Graphics Architecture - AGA chip set (or as it was then known, the AA, or Double-A chip set) for nearly a year. It was inevitable that information about new machines would leak out from less-reliable developers, so many of you would have read various rumours and 'Exclusives' in other magazines. While some are close, none of the reports I read were entirely accurate. At last the AGA has been announced, and developers are now allowed to talk about many things we have, up until now, not been able to talk about, including the AGA chip set, the Amiga 4000, Workbench 2.1, Workbench and Kickstart 3.0 and even the Amiga 600 (Commodore lawyers are not the fastest of people!)

First, I will briefly mention the two new Workbench versions, as I'm sure there are many of you who are worried about updating Kickstart yet again so quickly after upgrading to Kickstart 2.04.

Do not worry. Workbench 2.1 is a disk-only upgrade that replaces Workbench 2.04, it runs on Kickstart 2.04 perfectly. Workbench and Kickstart 3.0 are mainly new versions that support the AGA chipset, and will be included with the AGA machines, so if you have a non AGA chipset (ie every Amiga currently released!) you won't need it. Future Amiga software will support Kickstart 2.04, so if you haven't upgraded yet, don't worry about 2.1 or 3.0, buy Kickstart 2.04 now, you won't regret it!

AGA Chipset

So, on to the Advanced Graphics Architecture chipset. How does it compare to the original and the ECS graphics chips? Well, the ECS graphic chips offered few advantages over the originals, a new Super-Hires mode with 1280x256/512 resolution, and a flicker-free Productivity mode (640x480) but both with a limited palette of 64 colours.

The AGA chip is a total redesign of the chips. Gone are Denise and the seriously overweight Agnus, to be replaced by two new large ladies, Alice and Lisa. The chips are register-compatable with the original chipset, meaning most old software (including games) should run without problem on the AGA chips, but no doubt some programs will fail, there are so many changes to the chips that it's impossible to say they will be totally compatable.

The problem with adding screen modes before was due to the speed of the chips. The more colours on screen, the more data has to be accessed by the display chips to show the picture. This is why previously medium and high resolution were limited to 16 colours. Now, with AGA, the chips have been rebuilt from scratch and can, under certain conditions, move data up to four times faster than the original chips. This means that all modes can now display all different types of screen, including 32 colours, HAM, and Extra-Half-Bright. Along with this comes new modes (see Table 1) which include a true 256 colour mode (similar to VGA on a PC, but at higher resolution), and HAM-8, a new Hold and Modify mode that allows 64 base registers compared to 16 in normal HAM, these extra base registers can, with the right image creation software, almost totally get rid of the infamous HAM-fringing associated with these displays.

Currently the Amiga has a palette of 4096 colours to play with, this has now been improved to over 16 million (24-bit colour), although colours can still be chosen from the older 4096 palette for compatability with old software.

All modes, except VGA, are displayable on a standard monitor (Phillips 8833, 1084, etc), or even on a TV via a modulator. The chipset has a built-in deinterlacer for multisync monitors, which, in conjunction with Workbench 3.0 will 'promote' interlaced screens to the equivelant flicker-free version.

Dual playfield mode is now improved so you can have two 16 colour playfields (the standard chips have two 8 colour playfieds), and sprite colours can be defined seperately from the playfield colours.

Sprites themselves can now be 16 pixels wide (as standard), 32 pixels or 64 pixels, and sprites can be moved four times more smoothly (on Super-Hires pixels rather than Low-Res pixels), they can be low-res or high-res (no more blocky low-res mouse pointers), and can be displayed in the border.

How does AGA compare to the rivals, Super VGA PC's and the new Atari Falcon. Well, you'll be pleased to know that Atari Falcon can't match the higher resolutions of AGA, being limited to 640x480 maximum resolution. Most Super VGA cards can display 1024x768 in 256 colours, although this is rarely used, most people use 800x600 in 256 colours. Super Hires Interlace gives AGA up to 1280 x 512 in thousands of colours, and doesn't require an expensive VGA monitor to display it.

Standard mode for games on the PC is low-res VGA (320x200 in 256 colours). The equivelant AGA mode is 320x256 (a larger screen area), and with HAM-8 mode over 81,000 colours on screen are possible (ie. every pixel a different colour from a palette of 16 million).

With higher modes true photo-realistic displays are possible. I, for one, can't wait for Deluxe Paint 5 (or whatever) that will allow me to use the new modes. Some developers have had the new chipset machines for some time, so expect some good software support right from day one of launch.

So, how do you get the new AGA chipset? First the good news, Commodore plans to incorporate AGA into every new Amiga model they do, and improved versions are already on the drawing board allowing even more resolutions and faster access.

The bad news is that the chipset is now a 32-bit only chipset and will not work in any current Amiga, even the Amiga 3000. Don't blame Commodore for this, to get the vast improvement in the chips functionality they had to redesign everything. 32-bit means that it will require a 68020 or higher processor to run, and Commodore will probably opt for at least a 16Mhz 68030 chip in their new low-end machines.

Workbench 2.1

Workbench 2.1 is the new version of Workbench for Kickstart 2.04 users. Although mostly the same as Workbench 2.04 (many of the files are unchanged), there are several important changes.

1. Postscript printer support.

At last, decent Postscript printer support has been added. A new preference program, PrinterPS, allows any program that supports Preferences output to print to Postscript. PrinterPS allows control of fonts, spacing, page orientation, graphics printing and many more Postscript features.

2. Locale.library

Mainly of use to European Amiga users, this allows programs (including Workbench) to run with different languages. You set up your country preferences with the Locale program in Preferences and choose which languages you prefer. So, for example, if you prefer Italian, can understand French but want English only if neither Italian nor French are available you can set up your Locale preferences to tell software which language to use. Of course the programs you use must be programmed to support Locale, but that is relatively easy, and under Locale you can at least make many Dos and System error messages appear in the language of your choice.

3. Workbench Sounds.

You can have a custom sound sample instead of the standard System error beep under Workbench 2.1, so you can have Marvin the Paranoid Android saying "Oh no, not again", every time something goes wrong, if you want to.

4. CrossDOS.

The popular PC transfer package, CrossDOS, has been incorporated into V2.1. Now, by mounting PC0: you can access a 720Kb MS-DOS disk in DF0: You can set up translation tables to automatically convert MS-DOS Ascii files into Amiga Ascii.

5. Bullet.library

Compugraphic Font support has been beefed-up with the addition of Bullet.library, a full Amiga implementation of the Agfa Intellifont Compugraphic engine. This allows Compugraphic fonts to be scaled independently in x and y axes, sheared, rotated. kerned and much more. Although most of these features will not be immediately available until software supports it directly, it further enhances the font capabilities of the Amiga significantly.

Plenty of things have been cleaned up under Workbench 2.1, for example the format command no longer gives a "Formatting 1, 78 to go" message, but you get a status bar that shows graphically how far the format has proceeded.

Kickstart/Workbench 3.0

Although this is called Workbench 3.0, there are few differences between it and Workbench 2.04/2.1, at least on the surface. New Preferences programs allow you to have an IFF picture on your workbench backdrop instead of a pattern.

One major improvement is in the file system. A new version of the Fast File System, called DIrectory Caching File System (DCFS) is supplied. This allows floppy disks in particular to be accessed far faster, in particular the DIR command works faster. It claims that floppy disks are now as fast as hard drives, and hard drives are as fast as the Ram disk. I doubt these claims will reach the finished product!

Also included is DiskSalv V2.1, a new version of the popular (because it's the only one that ever worked properly) disk rescue software. The new version can do more to repair and validate faulty disks, and supports the new file systems supported under Kickstart 3.0.

The major work on Kickstart 3.0 was to provide operating system support for the new AGA chipset. There is a whole new set of OS calls (most of the graphics.library and intuition.library had to be completely re-written), which allow use of 256 colour workbench windows, with different applications sharing a common colour palette and other fun things.

Internal improvements allow a few new features for programmers, such as attached screens. You can attach two screens so they both scroll together (handy for programs like Deluxe Paint IV with a seperate palette screen). Screens can now be interleaved. This improves graphics performance (the blitter can move screen data in one blit rather than one blit per bitplane), although it confuses some programs (like Art Department Professional) that try to 'grab' the Workbench screen. Double-Buffering support for animation and games has also been added.

Intuition has been cleaned up yet again. The menu bar no longer remains white text on black, you can now define it to any pens used in the colour screen, and the default is black on white, far clearer than under 2.04. The Amiga key symbol in menu options and the tick are now scalable, so you no longer get a silly tiny Amiga key when using a big font.

Graphic tablets are now properly supported instead of just emulating a mouse. Exact position information can be returned, along with information on pressure, sub-pixel positioning and more. This will not work with all software, so programs (in particular paint packages) will have to be written to support these features directly.

          Table 1. New AGA Screen Modes

New Screen
                    Planes    Colours
LORES               6         64
(320x256)           7         128
                    8         256
                    8HAM      >81,000

LORES LACE          6         64
(320x512)           7         128
Interlaced          8         256
                    8HAM      >163,000

MEDRES              5         32
(640x256)           6EHB      32+32 shades
                    6HAM      4096
                    6         64
                    7         128  
                    8         256
                    8HAM      >163,000

HIRES               5         32
(640x512)           6EHB      32+32 shades
Interlaced          6HAM      4096
                    6         64
                    7         128  
                    8         256
                    8HAM      >327,000
          
SUPERHIRES          1         2    
(1280x256)          2         4
                    3         8    
                    4         16
                    5         32
                    6EHB      32+32 shades
                    6HAM      4096
                    6         64
                    7         128
                    8         256
                    8HAM      >327,000

SUPERHIRESLACE      1         2    
(1280x512)          2         4
Interlaced          3         8
                    4         16
                    5         32
                    6EHB      32+32 shades
                    6HAM      4096
                    6         64
                    7         128
                    8         256
                    8HAM      >655,000

VGA                 1         2
(160x480)           2         4
(320x480)           3         8
(640x480)           4         16
Non-Interlaced      5         32
                    6EHB      32+32 shades
                    6HAM      4096
                    6         64
                    7         128
                    8         256
                    8HAM      >76,000 (160),  
                              >153,000 (320), 
                              >307,000 (640)

Notes: Now all screen modes can use either the standard 4096 colour palette or the new enhanced 16M colour palette. Previously VGA and SuperHires were limited to 64 colour palettes.

8HAM - 8-bit HAM works in a similar mode to the original Hold and Modify, except it uses 64 24-bit base registers compared to 16 12-bit registers in the original HAM.