Atari XL/XE

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    The Atari 8-bit family is a series of 8-bit home computers manufactured from 1979 to 1992. All are based on the MOS Technology6502CPU and were the first home computers designed with custom coprocessor chips. Over the following decade several versions of the same basic design were released, including the original Atari 400 and 800 and their successors, the XL and XE series of computers. Overall, the Atari 8-bit computer line was a commercial success, selling two million units through its major production run between late 1979 and mid-1985.

 

Origins

        Design of the 8-bit series of machines started at Atari Inc. as soon as the Atari 2600games console was released in late 1977. The engineering team from Atari Grass Valley Research Center (originally "Cyan Engineering")felt that the 2600 would have about a three year lifespan before becoming obsolete. They started "blue sky" designs for a new console that would be ready to replace it around 1980, three years after the 2600's introduction. What they ended up with was essentially a "corrected" version of the 2600, fixing its more obvious flaws.The newer design would be faster than the 2600, have better graphics, and would include much better sound hardware. Work on the chips for the new system continued throughout 1978 and primarily focused on much-improved video hardware known as the Color Television Interface Adaptor, or CTIA.

        During this gestation the home computer era began in earnest in the form of the TRS-80, Commodore PET, and Apple II family—what Byte Magazine would later dub the "1977 Trinity" Ray Kassar, the then-new CEO of Atari from Warner Communications, wanted the new chips to be used in a home computer to challenge Apple. In order to adapt the machine to this role, it would need to support character graphics, include some form of expansion for peripherals, and run the then-universal BASIC programming language. The need for character graphics led to the introduction of the ANTIC, a co-processor that ran in concert with the CTIA to provide graphics. Like the earlier TIA of the 2600, the CTIA was designed to produce sprites and nothing else. ANTIC was built to generate conventional bitmap graphics and characters, providing a number of different modes with varying color support and resolution. ANTIC and CTIA worked in concert to produce the complete display.

 

 

The early machines: 400 and 800

      Management identified two sweet spots for the new computers, a low-end version known as Candy, and a higher-end machine known as Colleen (named after two attractive Atari secretaries).The primary difference between the two models was marketing; Atari marketed Colleen as a computer, and Candy as a game machine (or hybrid game console). Colleen would include slots for RAM and ROM, a second 8 KB cartridge slot, monitor output (including 2 more pins for separate luma and chroma) and a full keyboard, while Candy used a plastic "membrane keyboard" and internal slots for memory (not user upgradeable).

      At the time, the Federal Communications Commission (FCC) mandated that signal leakage in the television frequency range had to be extremely low. As the Atari machines had TV circuitry inside them, they were subject to this rule and needed to be heavily shielded. Both machines were built around very strong cast aluminum shields forming a partial Faraday cage, with the various components screwed down onto this internal framework. This had the advantage of producing an extremely sturdy computer, although at the disadvantage of being expensive and complex. The FCC ruling also made it difficult to have any sizable holes in the case, which eliminated expansion slots or cards that communicated with the outside world via their own connectors. Instead, Atari designed the Serial Input/Output (SIO) computer bus, a daisy-chainable system that allowed multiple devices to connect to the computer through a single shielded connector.

     Atari had originally intended to port Microsoft BASIC to the machine, as had most other vendors, intending to supply it on an 8 KB ROM cartridge. However the existing 6502 version from Microsoft was 12 KB, and all of Atari's attempts to pare it down to 8 KB failed. Eventually they farmed out the work to a local consulting firm, Shepardson Microsystems, who recommended writing their own version from scratch, which was eventually delivered as Atari BASIC.

      The machines were announced in late 1978 as the 400 and 800, although they weren't widely available until November 1979, much closer to the original design date. The names originally referred to the amount of memory, 4 KB RAM in the 400 and 8 KB in the 800. However by the time they were released the prices on RAM had started to fall, so the machines were instead both released with 8 KB. As memory prices continued to fall Atari eventually supplied the 800 fully expanded to 48 KB, using up all the slots. Overheating problems with the memory modules eventually led Atari to remove the module's casings, leaving them as "bare" boards. Later, the expansion cover was held down with screws instead of the easier to open plastic latches.

      The Atari 400, despite its membrane keyboard and single internal ROM cartridge slot, outsold the more feature rich Atari 800 by some margin. Because of this, developers were generally unwilling to use the 800-only right cartridge slot.

 

 

 

Liz

     The 400 and 800 were complex and expensive machines to build, consisting of multiple circuit boards mostly enclosed by massive die-cast aluminum shielding. Additionally, the machine was designed to add RAM only through cards, though it soon shipped fully expanded right from the factory. Soldering that RAM to the motherboard would be much less expensive than the connectors and separate cards needed in the 800. At the same time the 400 didn't compete technically with some of the newer machines appearing in the early 1980s, which tended to ship with much more RAM and an upgraded keyboard.

     Another major change was the introduction of the FCC ratings specifically for digital devices in homes and offices. One of the ratings, known as Class B, mandated that the device's RF emissions were to be low enough not to interfere with other devices, such as radios and TVs. Now computers needed just enough shielding to prevent interference (both ways), not prevent any emissions from leaking out. This requirement enabled lighter, less expensive shielding than the previous 400 and 800 computers.

     In 1982 Atari started the Sweet 8 (or "Liz NY") and Sweet 16 projects to take advantage of these changes. The result was an upgraded set of machines otherwise similar to the 400 and 800, but much easier to build and less costly to produce. Whereas the previous machines had individual circuit boards mounted inside and outside the internal shield, in the new design a single board supported all of the circuitry and the much thinner shielding was attached to it. This reduction in complexity was helped by improvements in chip making since the original machines were released, allowing a number of separate chips in the original systems to be condensed into one. Atari also ordered a custom version of the 6502, initially labeled "6502C" but eventually known as SALLY to differentiate it from a standard 6502C, which added a single pin that allowed four support chips to be removed. The SALLY was incorporated into late-production 400/800 machines, all subsequent XL/XE machines and Atari 5200/7800 game systems.

     Like the earlier machines, the Sweet 8/16 was intended to be released in two versions as the 1000 with 16 KB and the 1000X with 64 KB; RAM was still expensive enough to make this distinction worthwhile. In order to support expansion for high-end systems, similar to the card slots used in the Apple II or S-100 machines, the 1000 series also supported the Parallel Bus Interface (PBI), a single expansion slot on the back of the machine. An external chassis could be plugged into the PBI, supporting card slots for further expansion.AC

 

1200XL

  Released in late 1982, the 1200XL was an odd hybrid of features from the Sweet 8/16 projects. Notable features were 64 KB of RAM, built-in self test, redesigned keyboard (featuring four function keys and a HELP key), and redesigned cable port layout. In general terms the 1200XL most closely matched the "high end" Sweet 16 concept.

 

      However the 1200XL also included a number of missing or poorly implemented features. The PBI expansion connector from the original 1000X design was left off, making the design rely entirely on SIO again. Frustrating this was the fact that the +12V pin in the SIO port was left unconnected; only +5V power was available although some devices made use of the +12V line. An improved video circuit provided more chroma for a more colorful image, but the chroma line was not connected to the monitor port, the only place that could make use of it. Even the re-arrangement of the ports made some joysticks and cartridges difficult or impossible to use. Changes made to the operating system to support the new hardware also resulted in compatibility problems with some older software that did not follow published guidelines. The 1200XL ended up with functionality similar to the existing 800, but at a hefty price point. For all of these reasons the 1200XL sold poorly. There is an often-repeated story, perhaps apocryphal, that 800 sales shot up after the release of the 1200XL, as existing owners tried to snap them up before they disappeared. The machine was discontinued in 1983. There was no PAL version of the 1200XL.

 

 

 

Newer XL machines

     By this point in time Atari was involved in what would soon develop into a full-blown price war when Jack Tramiel of Commodore International was attempting to undercut his old enemy Texas Instruments. TI had undercut Commodore's calculator business only a few years earlier, almost driving him from the market, but this time Tramiel's supply was stronger than TI's, and he could turn the tables.

     Although Atari had never been a deliberate target of Tramiel's wrath, they, along with the rest of the market, were dragged into "his" price war in order to maintain market share. The timing was particularly bad for Atari; the 1200XL was a flop, and the earlier machines were too expensive to produce to be able to compete at the rapidly falling price points. The solution was to replace the 1200XL with a machine that users would again trust, while at the same time lowering the production costs to the point where they could compete with Commodore.

    Starting with the 1200XL design as the basis for a new line, Atari engineers were able to add a number of new IC's to take over the functions of many of those remaining in the 1200XL. While the 1200XL fit onto a single board, the new designs were even smaller, simpler, and as a result much less expensive. But by this point, in early 1983, the price war rapidly drove prices downward. Atari, attempting to beat this downward pressure, took the opportunity to move production of the new machines to the far east, where they could be produced for even lower costs.

 

           

 
       
Atari 600XL.   An Atari 800XL  

 

         Several versions of the new design, the 600XL, 800XL, 1400XL and 1450XLD were announced at the 1983 Summer CES. The machines had Atari BASIC built into the ROM of the computer and the PBI at the back that allowed external expansion. The machines looked similar to the 1200XL, but were smaller back to front, the 600 being somewhat smaller than the 800 front-to-back (similar to the original Sweet 8 project). The 1400 and 1450 both added a built-in 300 baud modem and a voice synthesizer, and the 1450XLD also included a built-in double-sidedfloppy disk drive in an enlarged case.However, the production move ran into unexpected delays. Originally intended to replace the 1200XL in mid-83, the machines did not arrive until late in 1983. Although the 600/800 were well positioned in terms of price and features, during the critical Christmas season they were available only in small numbers while the Commodore 64 was widely available. Although the 800XL would be the most popular computer sold by Atari, it was unable to defend Atari's marketshare, and the race to the bottom gutted their profits. Combined with the simultaneous effects of the video game crash of 1983, Atari was soon losing millions of dollars a day. Their owners, Warner Communications, became desperate to sell off the division.

        Through this process the 1400XL and the 1450XLD had their delivery dates pushed back, first by the priority given to the 600XL/800XL, and later by the 3600 System. In the end the 1400XL was eventually canceled outright, and the 1450XLD so delayed that it would never ship. Other prototypes which never made it to market include the 1600XL, 1650XLD, and 1850XLD. The 1600XL was to have been a dual processor model capable of running 6502 and 80186 code, while the 1650XLD was a similar machine in the 1450XLD case. These were canceled when James J. Morgan became CEO and wanted Atari to return to its video game roots. The 1850XLD was to have been based on the Amiga Lorraine (later to become the Commodore Amiga). These models were canceled when Jack Tramiel took over Atari and changed the XL series development into the XE series. The new Atari scrapped plans for the Amiga-based 1850XLD system for the Atari ST system.

       Although Commodore emerged intact from the computer price wars, fighting inside Commodore soon led to Jack Tramiel's ousting. Looking to re-enter the market, he soon purchased Atari consumer division from Warner for an extremely low price.

 

 

Tramiel era: XE series and XE Game System

 

      Jack Tramiel's Atari Corporation produced the final machines in the 8-bit series, which were the 65XE and 130XE (XE stood for XL-Expanded). They were announced in 1985, at the same time as the initial models in the Atari ST series, and visually resembled the Atari ST. Originally intended to be called the 900XLF, the 65XE was functionally equivalent to the 800XL minus the PBI connection. The 65XE (European version) and the 130XE had the Enhanced Cartridge Interface (ECI), which was electronically almost compatible with the Parallel Bus Interface (PBI), but physically smaller, since it was located next to the standard 400/800-compatible Cartridge Interface and provided only those signals that did not exist in the latter; ECI peripherals were expected to plug into both the standard Cartridge Interface and the ECI port. The 130XE shipped with 128 KB of memory, accessible through bank-selection.

       An additional 800XE was available in Europe (mostly Eastern Europe), which was essentially a 65XE repackaged in order to ride on the popularity of the original 800XL in Europe. Unfortunately, the 65XE and 800XE machines sold in Eastern Europe had a buggy GTIA chip, specifically those machines made in China in 1991.

        Finally, with the resurgence of the gaming industry brought on by Nintendo, Atari Corp. brought out the XE Game System (XEGS), released in 1987. The XE Game System was sold bundled with a detachable keyboard, a joystick and a light gun (XG-1), and a couple of game cartridges (Bug Hunt and Flight Simulator II). The XE Game System was essentially a repackaged 65XE, and was compatible with almost all Atari 8-bit software and hardware as a result. Bad marketing and a lack of newer releases hampered sales.

On January 1, 1992, Atari corp. officially dropped all remaining support of the 8-bit line.

 

 
 
Atari XE Series       Atari XE Game System
         

 

 

 

Design

       The Atari machines consist of a 6502 as the main processor, a combination of ANTIC and GTIA chips to provide graphics, and the POKEY chip to handle sound and serial input/output. These "support" chips are controlled via a series of registers that can be user-controlled via memory set/get instructions running on the 6502. For example, the GTIA uses a series of registers to select colors for the screen; these colors can be changed by inserting the correct values into its registers, which are mapped into "memory" that is visible to the 6502. Some parts of the system also use some of the machine's RAM as a buffer, notably the ANTIC's display buffer and its Display List (essentially a small program written in the chip's simple machine language that tells ANTIC how to interpret that data and turn it into a display), as well as GTIA's sprite information. These features enable the computer to perform many functions directly in hardware, such as smooth background scrolling, that would need to be done in software in most other computers of the time.

 

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