Archive for August, 2015

Atari ATW800

August 16, 2015

There are rare computers and there are very rare computers, and there are computers that are extremely hard to come by. Recently, almost by accident, I was able to acquire one of the latter, one that I always (since the time you could actually buy it as a brand new product) wanted to have. It looks gorgeous, even nowadays, because it is basically a steel case where the colour is not ageing (and because it comes from a collector that obviously took very good care for this machine). But enough rambling, let’s look at my precioussss…

The Atari Transputer Workstation (also known as ABAQ, ATW-800, or simply ATW) was a workstation class computer released by Atari in 1989, based on the INMOS Transputer.

As some of you might remember, Transputers were considered to be the Next Big Thing in the late 1980s. Transputers wanted to solve the problem of increasing the performance of a computer system without the need of having to develop faster CPUs (which was already then considered to be economically feasible only up to a certain limit. This limit was reached in a way in 2001). Instead, an arbitrary number of cheap but complete CPUs should collaborate to provide the needed performance. Sounds familiar? Yes, its basically the same concept as multi-core machines today with the difference that Transputers were separate chips that also did not share caches. As the collaboration of CPUs was very important for this approach fast (for the time) interconnections between the Transputers were built into each of them that could extend even outside a single computer system and therefore connect multiple Transputer computers to a combined system. Transputers contained a built-in RAM controller, so RAM could be added easily.
Transputers were the product of a single British company, Inmos that released the first Transputer in 1985. Transputer systems could not hold up to their more traditional competition, and in 1989 Inmos was sold to SGS Thomson. After that, Transputers were basically discontinued.

Inmos designed these Transputer CPUs models in it’s lifetime:

name clock word remarks
T212 17.5, 20 MHz 16 bit
M212 17.5, 20 MHz 16 bit with on-board disk controller
T222 20 MHz 16 bit
T225 20 MHz 16 bit
T414 15, 20 MHz 32 bit
T425 20, 25, 30 Mhz 32 bit
T400 20 Mhz 32 bit stripped-down T425
T800 20, 25 MHz 32 bit 64 bit floating point support
T801 20, 25 MHz 32 bit 64 bit floating point support
T805 20, 25, 30 Mhz 32 bit 64 bit floating point support

The ATW and its operating system, HeliOS, was conceived by Perhelion, a company that was founded by former employees of MetaComCo. As MetaComCo had good connections to both Atari and Commodore, Perhelion tried to interest both companies in releasing a Transputer workstation running HeliOS. Commodore had expressed some interest in their new system, and showed demos of it on an add-on card running inside an Amiga 2000. It appears they later lost interest in it. It was at this point that Atari met with Perihelion and work started on what would eventually become the ATW.

The machine was first introduced at the November 1987 COMDEX under the name Abaq. Two versions were shown at the time; one was a card that connected to the Mega ST bus expansion slot, the second version was a stand-alone tower system containing a miniaturized Mega ST inside. The external card version was dropped at some point during development. It was later learned that the “Abaq” name was in use in Europe, so the product name was changed to ATW800.

The ATW system came in a large tower case. It consisted of three main parts:

  • the main motherboard containing a T800-20 Transputer and 4MB of RAM (expandable to 16MB)
  • a complete miniaturized Mega ST acting as an I/O processor with 512kB of RAM
  • the Blossom video system with 1MB of dual-ported RAM

All of these parts were connected using the Transputer’s 20 Mbit/s processor links. The motherboard also contained three slots for additional “farm cards” containing four Transputers each, meaning that a fully expanded ATW contained 13 Transputers. The bus was also available externally, allowing several ATWs to be connected into one large farm. The motherboard also included a separate slot for one of the INMOS crossbar switches to improve inter-chip networking performance.

HeliOS was Unix-like, but not Unix. Of particular note was the lack of memory protection, due largely to the lack of an MMU on the Transputer. This is not quite the issue it might seem, as the Transputer’s stack-based architecture makes an MMU less important. Meanwhile HeliOS was Unix-like enough that it ran standard Unix utilities, including the X Window System as the machine’s graphical user interface (GUI). In addition HeliOS ran on all of the Transputers in a farm at “the same time”, which allowed all computing tasks to be fully distributed. Turning off an ATW would not affect the overall farm, the tasks would simply move to other processors on other systems. Later HeliOS was ported to other processors including the ARM architecture.

The Blossom video system was developed specially for the ATW. It offered 4 different video modes up to 1280 by 960 pixels at 16 out of 4096 colours. The Blossom also included a number of high-speed effects (128 megapixels/s fill rates) and blitter functionality, including the ability to apply up to four masks on a bit-blit operation in a fashion similar to a modern graphics processing unit’s ability to apply several textures to a 3D object. The team in charge of the Blossom would later work on another Atari project, the Atari Jaguar video game console.

There is an ATW price list in Pound Sterling (GBP) stating the prices for the machine and various options excluding VAT:

Product Price Education Price
ATW 5000 2500
Farm Card 2000 1500
+4MB RAM 750 562
Expansion 500 375

5000 GBP in 1990 equals to about 13700 DEM or 8000$ at the time which corresponds about 9900 GBP or 14000$ today. Quite a price… On the other hand, an Atari TT was 3000$ in 1990.

It took quite long in a PC before a machine could handle more than 4 processors or cores.

I also looked into how the ATW compares to other product-level Atari computers in terms of speed. MIPS-wise, a corresponding list looks like this:

model clock CPU MIPS year
ST 8MHz 68000 1 MIPS 1985
MegaSTE 16MHz 68000 2 MIPS 1991
Falcon 16MHz 68030 3.84 MIPS (Motorola DSP: 16 MIPS) 1992
TT 32MHz 68030 8 MIPS (I guess because is runs at 2*16MHz) 1990
ATW 20MHz T800-20 10 MIPS (per T800, i.e. 130 MIPS for 13 T800-20) 1989

One can argue that the DSP inside the Falcon has a quite hefty 16 MIPS, and that a combined 20 MIPS for the Falcon (CPU + DSP) is more than the combined 11 MIPS of the ATW, but first, a DSP is not a general purpose processor, so this power is not available to every program. Second, you could add up to 12 T800-20 inside an ATW… So, although the ATW did not run TOS, and it therefore not the fastest ST that has been sold by Atari, it was the fastest computer by Atari. Of course, later projects (e.g Hades) would have been much faster.If we look at the cost per MIPS, we can state the following:

model cost per MIPS configuration
TT 375$
ATW 800$ no farm card
ATW 240$ 1 farm card
ATW 135$ 3 farm cards

So, if you needed to have compute power, a loaded ATW was an economic option.It is said that only between 200 and 350 ATWs have been built, out of which 50 to 100 were prototypes that were released already in in May 1988. The production run has been released in May 1989. Another rumour is that 200 ATWs were sold to Kodak. The label on the back of an ATW say something like:

Serial Number: AB84A 90XXXX

The serial numbers that I know are:

  • 909131
  • 909215

It says also: Made In Germany. That sounds unusual. It probably means that the ATW was assembled by a 3rd party.If you have ever heard of Transputers outside this text, it was probably a long time ago. This effect typically indicates that a technology was not successful as it is also the case here. For the ATW 800 there are three groups of reasons for the failure of this machine:

  • this machine was ways too pricey for the mass market
  • Atari seem not to have invested much time and effort in supporting this model or to develop successors (I can also imagine they made a loss on every machine)
  • HeliOS was a too exotic environment
  • Perihelion remained the exclusive distributor in England (and it was always a small company)
  • Transputers as a technology failed because they had problems in terms of pricing, and later on performance compared to the (traditional) competition
  • Inmos as the sole manufacturer of these CPUs was a too small company
  • finally, Inmos folded basically in the same year as the ATW was published

Still, despite the failure of the machine for the masses (:-)), the ATW 800 was a good computer and had the potential to be used advantageously in some niches like scientific computing. A running ATW 800 is still the best opportunity to experiment with the Transputer technology. If you can get one, that is. It is rare to a ridicule degree.Technical Data

  • CPU: Inmos T800-20 @20 MHz (10 MIPS)
  • RAM: 4MB (expandable to 16MB)
  • HDD: 44MB
  • OS: HeliOS
  • Graphics: Blossom video system with 1MB of dual-ported RAM, supporting
    • mode 0: 1280 by 960 pixels, 16 colours out of a palette of 4096 (including 16 true greyscales, on a monochrome monitor)
    • mode 1: 1024 by 768 pixels, 256 colours out of a palette of 16.7 million
    • mode 2: 640 by 480 pixels (2 virtual screens), 256 colours out of a palette of 16.7 million
    • mode 3: 512 by 480 pixels, 16.7 million colours
  • Interfaces: RGB component display interface
  • Contains: a miniaturized Mega ST with 512kB RAM with all its interfaces
  • Released: May 1989
  • Number of produced machines: between 200 – 350 (of which 50 – 100 were prototypes)
  • Initial price: 5000 GBP

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