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© 1997-2006
Gareth Knight
All Rights reserved

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The AAA Chipset

The AAA Chipset
The AAA (Advanced Amiga Architecture)chipset was a secret project initiated by Commodore around 1989 to create the next generation of Amiga technology. Development on it continued until 1993 until it was abandoned in favour of Hombre. Since then it has fallen into a mythical state that has led Amiga users to believe an Amiga based upon this design could turn the Amigas fortune around. In an online conference on March 6th, 1996 discussed the AAA chipset:
First of all, the AAA chipset was never finished. We had prototypes that were flawed, but did some real stuff, though they weren't functional enough to run the OS. New revisions of each of the four chips had been taped out. The AAA chipset was a 32/64-bit implementation of the Amiga architecture. It maintained as much register-level compatibility as possible with the OCS chipset, while adding zillions of 32-bit registers.
As the name indicates, AAA was designed as a followup to the AA chipset (AA was renamed AGA at a later date). Despite a similar philosophy behind the two designs, AAA shares little with the AGA chipset. The AGA was created as an evolution of the OCS and ECS before it- most software designed for OCS will run on the AGA. The AAA was a clean break from the past with an all new architecture consisting of four VLSI integrated circuits. Some compatibility is obtained by the processor being register compatible. The designers believed AmigaOS 3 provided significant control over the custom chips that no one would "bang the metal", allowing the software to run on the AAA chipset. Unlike previous chipset that provided both high and low-end solutions, AAA was entirely modular allowing it to be scaled to the level required.

Improvements

The AAA improved on previous efforts in a number of ways. One problem that was found with AGA was that some functions could not be implemented properly because of the pressure to remain as close to the ECS design as possible. The AAA abandons this philosophy implementing a forward looking design. This improved on a number of areas, memory and CPU bandwidth are improved. In its design, AAA is only 1.14 times faster than AGA the real performance improvement comes from the use of VRAM preventing display fetches from affecting access to the blitter, copper, etc.

The Chip RAM and Fast RAM distinction still remained but was improved on considerably. Chip Ram access was boasted to be faster than Fast Ram access on current systems. DMA access is dynamically handled but still remains disappointing. When too many tasks are in operation the display would not have been updated. This was acceptable at the time but now seems strange when compared to the latest hardware architecture.

The Blitter had been improved using pixel addressing rather than the familiar masks. This may be meaningless but makes it easier to program. Several tweaks of the Blitter design also allowed it to move data around faster. The Dave Haynie archive indicates performance increases by 6x when scrolling a 640x200x2 screen.

The Copper had been upgraded to handle 32-bit operations for the new 32-bit registers found in the AAA. Interrupt capability was also added allowing it to handle a series of blitter operations without additional CPU usage. This is an advancement on the custom chip philosophy by allowing different processors to perform seperate tasks.

The AAA adds five new pixel types, including a Chunky mode. Before the new chipset all Amiga systems used a Planar mode as standard, with the possible exception of the CD32 which added a workaround, using hardware Chunky to Pixel conversion. The new modes also allowed the addition of a video input, such as a frame grabber. It was not until 1998 that PC manufacturers caught up with this and finally offered an TV-compatible input.

The familiar Amiga architecture completely integrated both graphic, sound and floppy control into the custom chips. However, this meant that any upgrade to the Amiga architecture would be quite difficult. The AAA floppy controller was expanded to handle CD-ROM formats, increasing data I/O to 11.4MBit/second. Compatibility with original Mac 400k disks was also promised. Only the Catweasel and the Amiga OCS chipset approach its flexibility.

The Name Game

Vintage Amiga users will know the story behind the chipset names (see Amiga history). This tradition had been continued in the AAA using new names to refer to the four new chips.

Andrea Chip

Andrea was responsible for chip bus controller at the heart of the chipset, replacing Andrea. It controls all Chip RAM activity, manages the chip bus and video display clocks and video timing control. It also contains the AAA Blitter.

Linda Chip

Linda is a double-buffered line buffer, which makes it possible to run pixels and the chip bus at differen clock rates, and also does some compression tricks. The 64-bit AAA system uses two Linda and Monica chips.

Mary Chip

Mary took the place of Paula in the AAA design. It was the peripheral chip responsible for floppy disk, audio and serial I/O. Dave Haynie, one of the AAA creators described the Mary chip in greater depth on the Team Amiga Mailing List (6/5/99).
Of course, Mary did other stuff, too. The floppy controller was way more
flexible than anything anyone has ever done, far as I know, in the
interest of "floppy controller". As well as dealing with the standard raw
bitstream, Paula-style, it could handle this same thing at 2x or 4x
rates. It could also do on-the-fly MFM decoding in hardware, for PC-style
low-level sectored formats. It could also do CD or digital packet radio
formats. Data rates fast enough to handle 1x CD-ROM, 10-Base Ethernet, or
even the old ST-506 style hard disc, if you wanted it. Naturally, there
were already needs for faster CD/HD interfaces at the time, but this was
a far more interesting floppy controller than before.
A few days earlier (4/5/99) he went into detail on Mary's feature list and some of the changes the AAA design went through.
The Mary audio subsystem supported eight channels at up to 16-bit per
sample and CD-class sample rates. You could assign any channel to "left"
or "right", but otherwise, a fairly basic expansion of the original Amiga
audio idea, improved by the faster 32-bit chip bus. The audio is
digitally mixed to 18-bit, with an optional divide-by-2 or divide-by-4
scaling. On-chip DACs support 16-bit output (no guess to the quality, the
AAA chips were never far enough along to test any Mary features), though
there was a digital serial output, supposedly an easy hookup to a fairly
cheap CD-player style DAC.

Monica Chip

Monica is the AAA equivalent to Denise and Lisa on the previous chipsets, functioning as a display controller chip, displaying the timing data generated by Andrea and graphics data fetched by Linda. It is responsible for chunky and planar modes, HAM/HAM8, true colour and 10-bit HAM mode for 24-bit display.

View labelled prototype (47.3k)

Single System AAA

The single system AAA chipset consists of one of each of the four AAA chips and uses VRAM.
Single System AAA
Of particular interest is the Pixel Bus Slot located third from the top right of the image.This allows an AAA frame grabber to be attached. The data goes through Linda and is stored by Andrea. The Single AAA system also supports the implementation of an AGA video slot. However, compatibility with all devices is not guaranteed as many units depend upon the exact display rate of the AGA system.

Dual System AAA

Unlike previous Amigas, the Commodore engineering created the AAA chipset to support high and low-end features. The dual AAA includes all four of the AAA chips, plus an additional Linda and Monica. The display bus is also increased to 64-bits. The Linda and Monica chips handle even and odd pixel, increasing the speed of display.
Dual AAA system

Other information provided by Dave Haynie about AAA

The description of the AAA features come from a Team Amiga posting:
Chip RAM can be DRAM or VRAM; VRAM runs pixels twice as fast and eliminates display DMA from the chip bus proper. A 64-bit VRAM system can run 1280x1024 at around 11-12 bits/pixel at 60Hz, and many other resolutions are possible, including all your AA favorites. The system supports planar displays to 16-bit, as well as chunky displays, HAM8, HAM10, and HAM8-chunky. The 8 sprites still exist, and can go up to 128-bits wide. There's also a single bit overlay, and you can have dual 8-bit playfields too. 24-bits/pixel is supported as "byte-planes", which we called "hybrid" pixels (a little chunky, a little planar). The blitter and copper do 32-bit as well as the old 16-bit stuff. 32-bit blits are pixel addressed, and there are new blitter operations, like add, add with saturation, sort, and tally. Blits can use long bursts, so you get 32-bits moved in 70ns, rather than today's 16-bits moved in 280ns. The copper has a move multiple instruction, and a blitter interrupt (eg, copper lists can very cleanly feed the blitter new instructions). The audio supports 8 channels, 16-bits/sample with rates up to some 100kHz. Channels don't pan, but can be assigned left or right. No synthesis is available on-chip. Audio output can be divided by 2 or 4 to avoid clipping in the mix, and an 18-bit digital ouput is also available. Floppy handles standard 1MB, 2MB, and 4MB discs with or without real sectors. It also handles the CD-ROM encoding, RLL, and some digital radio format. It's technically fast enough for 1x CD-ROM or ST-506 hard disks. There are two buffered serial ports.

Where was AAA going?

Architecture for a modular AAA systemTowards the end of the AAA development process the design was becoming increasingly modular. The engineering team were anxious to move away from the Commodore tradition of locking users into specific hardware. It did not help the user and only gave the company a bad reputation, third parties would eventually work around the problem but would pass the expense onto the consumer. The Commodore Engineering developed an entirely modular system of upgradeable pieces, consisting of the motherboard, Chipset module, host processor module and Open System Bus Slots. The system bus would also be processor-independent allowing it to be upgraded over time without any performance loss. Previous experiences in trying to develop the A3000 architecture to the faster A4000 systems had shown the engineering team of the need to develop a system for a range of processors, rather than hacking the existing design each time. Examining the main sections of the motherboard in turn:

The Chip Module represented a move away from placing the custom chips on the motherboard. This would allow them to be upgraded as time progressed through simple plug-in expansion. Many would suspect this would have led to the Amiga chips being faded out in favour of industry standard designs such as the Voodoo Banshee. The only problem with this approach is the fact that the custom chips perform more than just graphical output, it also handles sound, floppy control, etc. However, it would be a step closer to an Amiga on a chip bringing the cost down dramatically.

The Expansion Controller does conversions to/from the Zorro protocols. This could be located on the motherboard on tower units or on the system bus module for the desktop. The modularity of this system would mean that, if the system was aimed at the low-end, the Controller could be left off.

The concept behind Open System Bus Slot seems to be basically a general purpose expansion, similar to the AGP on Pentium 2 motherboards. Two or three processor slots will be available for high-speed expansion, for the connection of DSPs or setting up a processor farm.

Could AAA be released today?
One of the big questions that many Amiga users ask is would it be possible to release an upgraded Amiga based upon the AAA chipset. They were almost finished and, unlike many other designs, is compatible with Amiga ECS. Dave Haynie, a former Commodore engineer and creator of the AAA chipset takes an impatient view of such an idea.

Gateway/AI would have been insane to continue AAA. It would have been
revolutionary if released in 1990, pretty cool in 1992, ok in 1994 (the
earliest it could have been released on the schedule we had, with a
healthy Commodore). Today, it would be a horribly expensive thing with
less graphics performance than any old everyday $10 PCI-based SVGA
graphics chip. There is simply no point whatsoever. And that's spelled
"HAYNIE"...
- Dave Haynie, Team Amiga ML, 3/5/99.

 

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