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.
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.
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?
 Towards 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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