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The Atari 8-bit family is a series of 8-bit Home Computer s manufactured by Atari , starting in 1979. All are based on the MOS Technology 6502 CPU 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. HISTORY Origins Design of the 8-bit series of machines started as soon as the Atari 2600 Games Console was released in late 1977. The engineering team from Atari's Grass Valley Research Center (who called themselves ''Cyan Engineering'') felt that the 2600 would have about a three year lifespan before becoming obsolete, and started "blue skying" designs for a new console that would be ready to replace it around 1980. What they ended up with was essentially a "corrected" version of the 2600, fixing its more obvious flaws. 3 Generations of Game Machine Architecture 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 Adapter'', or CTIA. During this gestation the home computer revolution "took off" in the form of the Apple II Family , Commodore PET and TRS-80 . Ray Kassar, the then-new CEO of Atari from Warner Communication s, 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 Peripheral s, and run the then-universal BASIC Programming Language . Management identified two Sweet Spot s for the new computers, a low-end version known as Candy, and a higher-end machine known as '''Colleen''' (rumored to be named after attractive Atari staff). 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 8k cartridge slot, Monitor Output and a full keyboard, while Candy used a plastic " Membrane Keyboard " and internal slots for memory (not user upgradable). Both machines were very sturdy with huge internal aluminum shields, originally to meet FCC rules for TV signals emitted in RF space.
The early machines: 400 and 800 The machines were announced in December 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 released with 8 KB and 16 KB respectively. Due to the FCC restrictions, the 400/800 couldn't allow slots like those found on the Apple II computers. Instead, they created a proprietary, expensive serial interface called Serial Input/Output (SIO). All external devices were connected using this interface in a daisy-chain fashion. On the 800, the internal slots were reserved for ROM and memory modules. Originally the 800 shipped with 16 KB, but as memory prices continued to fall Atari eventually supplied the machines fully expanded to 48 KB, using up all the slots. Overheating problems with the memory modules eventually led Atari to remove the modules 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 800 was a complex and expensive machine to build, consisting of multiple circuit boards in various locations inside or outside the massive aluminum shield. Additionally, the machine was designed to add RAM only through cards, which required expensive connectors and packaging even though it soon shipped fully expanded right from the factory. 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 a real 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 address these issues. 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. Improvements in Chip Making allowed a number of chips in the original systems to be condensed into one. For comparison, the original 800 used seven separate circuit boards while the new machines used only one. Atari also ordered a custom version of the 6502, the "C" model, which added a single pin that allowed four support chips to be removed. An external expansion chassis was also supported. 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. 1200XL When the machines were actually released there was only one version, the 1200XL, 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 expansion connector from the original 1000X design was left off, making the design rely entirely on SIO again. Frustrating this was the fact that +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. There was no PAL version of the 1200XL. 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. |
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