Bits are modifiers for Playfield Mode instructions in bits Modifier bit value 1 Enables the modifier, and 0 disables the modifier. When horizontal scrolling is enabled ANTIC retrieves more screen memory bytes than displayed in order to show partially scrolled display bytes at the beginning and end of the line. Scrolling in Wide screen will cause blank data to be shifted into the scrolled area. The first Mode line without the VS bit set becomes the end of the scrolling region and is used as a buffer line to supply the new information to scroll up into the bottom of the scrolling region. The Character or Map mode specified will begin displaying bytes from that address.
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Origins[ edit ] Design of the 8-bit series of machines started at Atari as soon as the Atari games console was released in late While designing the in , the engineering team from Atari Grass Valley Research Center originally "Cyan Engineering"  felt that the 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 Work on the chips for the new system continued throughout and focused on much-improved video hardware known as the CTIA the version was the TIA.
Kassar felt the chipset should be used in a home computer to challenge Apple. All on-screen graphics are created using Player-Missile graphics sprites and a simple background using fixed patterns. The CTIA was designed on the same model, and likewise mainly used sprites for drawing. Commodore was developing their own video driver in-house at the time, but Chuck Peddle , lead designer of the used in the and the new machines, saw the Atari work during a visit to Grass Valley.
He realized the Commodore design would not be competitive but he was under a strict non-disclosure agreement with Atari, and was unable to tell anyone at Commodore to give up on their own design.
The slots are molded into the cast aluminum RF shield. Management identified two sweet spots for the new computers: a low-end version known internally as "Candy", and a higher-end machine known as "Colleen" named after two Atari secretaries.
Atari would market Colleen as a computer and Candy as a game machine or hybrid game console. At the time, plans called for both to have a separate audio port supporting cassette tapes as a storage medium. One executive stated, "Does the end user care about the architecture of the machine? The answer is no. The operating system boots automatically, loading drivers from devices on the serial bus SIO. The DOS system for managing floppy storage was menu-driven. When no software is loaded, rather than leaving the user at a blank screen or machine language monitor, the OS goes to the "Memo Pad" mode allowing the user to type a la the TV Typewriter using the built-in full-screen editor.
There was a running argument about whether the keyboard would be external or built in. While the Colleen design was largely complete by May , it was not until early that the decision was made that Candy would also be a complete computer, but one intended for children.
As such, it would feature a new keyboard designed to be resistant to liquid spills. The company contracted with local consulting firm Shepardson Microsystems to complete the port. A device known as an RF modulator is normally used for television output, and these are difficult to shield to the levels being mandated by the FCC.
The FCC required the entire device generating the signals to be tested as a whole, but as the RF modulator was sold by a 3rd party it was not considered to be part of the Apple II and could pass testing on its own. TI was in the home district of the current speaker of the house , Jim Wright , and the issue blew up into a minor political battle. Both 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 added manufacturing expense and complexity. The internal slots were reserved for ROM and RAM modules; they did not have the control lines necessary for a fully functional expansion card, nor room to route a cable outside the case to communicate with external devices.
Further drops in memory prices during led to both machines shipping with completely maxed-out RAM; 16k and 48k respectively, using 16kx1 DRAMs. The user-installable RAM modules in the initially had plastic casings but this proved to have overheating issues especially since the triple-voltage DRAM used at this time naturally tended to run hot, so the casings were removed.
Later, the expansion cover was held down with screws instead of the easier to open plastic latches. Paddle controllers were wired in pairs, and eight players could play Super Breakout.
Calling Atari "the videogame people", it went on to state they came with "some fantastic educational, entertainment and home applications software". He described the machine as "something else" before criticizing the company for a lack of developer documentation. It weighs about ten pounds The large amount of engineering and design in the physical part of the system is evident". Atari also ordered a custom version of the , initially labelled "C," but eventually known as SALLY to differentiate it from a standard C.
In order to support expansion for high-end systems, similar to the card slots used in the Apple II or S machines, the 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. 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. Considered as a whole, the differences between the and earlier machines was minor, or even retrograde. The has met with nearly universal insouciance in the microcomputer community, and for good reason.
It has an extra 16K in a designer case, without a right cartridge slot, expansion slots, or a third and fourth controller jack. It has no standard parallel or RS ports. Only substantive price cuts will help its image in any tangible way. Quite honestly, it depends entirely on what the price of the machine is. However, the indications are that the price of the will be dropped and that the will cost more than the If so, buy an quick!
There is an often-repeated story, perhaps apocryphal, that sales rose after the release of the XL, as people bought them before they disappeared. This machine had a slightly shallower case than the XL, as it lacks one row of RAM chips at the back of the case. By this point in time Atari was involved in what would soon develop into a full-blown price war.
Several years earlier, Commodore was a major calculator vendor, selling designs based on a Texas Instruments TI chipset.
TI decided to enter the market themselves and suddenly raised the prices to other vendors, nearly putting Commodore out of business. To ensure this would not happen again, Jack Tramiel of Commodore International purchased MOS Technology to ensure his supply of the for his computers. When TI introduced the TI, Tramiel turned the tables on them by pricing his machines below theirs. A price war ensued, causing a dramatic decline in home computer prices, reducing them as much as eight times over a period of a few months.
The timing was particularly bad for Atari; the XL was a flop, and the earlier machines were too expensive to produce to be able to compete at the rapidly falling price points. The machines looked similar to the XL, but were smaller back to front, the being somewhat smaller as it lacked one row of memory chips on the PCB. The high-end XL added a built-in baud modem and a voice synthesizer , and the XLD also included a built-in double-sided floppy disk drive in an enlarged case, with a slot for a second drive.
Their owners, Warner Communications , became desperate to sell off the division. The XL was to have been a dual-processor model capable of running and code, while the XLD was a similar machine in the XLD case. These were canceled when James J. Morgan became CEO and wanted Atari to return to its video game roots. Looking to re-enter the market, he purchased the Atari consumer division in July from Warner for an extremely low price.
This included the Amiga-based XLD system and other existing prototypes while Tramiel focused on developing the based Atari ST system and bringing in ex-Commodore engineers to work on the ST line. Six years is a pretty long time for a computer to last. The magazine stated that while its software library was comparable in size to that of other computers, "now—and even more so in the future—there is going to be less software being made for the Atari 8-bit computers", warning that only saw a "trickle" of major new titles and that "will be even leaner".
Companies stated that one reason for not publishing for Atari was the unusually high amount of software piracy on the computer, partly caused by the Happy Drive. It certainly looks like it might be from where I write",  and in MicroProse explicitly denied rumors that it would release Gunship for the Atari, stating that the market was too small. Product unavailability is especially severe for the 8-bit Atari".
They were announced in , at the same time as the initial models in the Atari ST series, and visually resembled the Atari ST. The XE was aimed to appeal at the mass market. The quality of the PCBs was poor, with thin, easily damaged wire traces, and most machines were equipped from the factory with Micron Technologies 64kx1 RAM chips, which had a high failure rate.
Most of the games were older titles, such as Necromancer and Blue Max both originally published by Synapse , not Atari , ported to cartridge format. Production timeline dates retrieved from Atari 8-Bit Computers F. Datasoft was one of the last significant North American companies to develop Atari 8-bit software, continuing to put out new games for them until the company closed its doors in 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 the address space that is visible to the The custom hardware features enable the computers to perform many functions directly in hardware, such as smooth background scrolling, that would need to be done in software in most other computers.
An instruction adds one row of the specified graphics mode to the display. Each mode varies based on whether it represents text or a bitmap, the resolution and number of colors, and its vertical height in scan lines.
An instruction also indicates if it contains an interrupt, if fine scrolling is enabled, and optionally where to fetch the display data from memory.
Since each row can be specified individually, the programmer can create displays containing different text or bitmapped graphics modes on one screen, where the data can be fetched from arbitrary, non-sequential memory addresses. Once the display list is set-up, the display is generated without any direct CPU intervention. There are 15 character and bitmap modes. In low-resolution modes, 2 or 4 colors per display line can be set. In high-resolution mode, one color can be set per line, but the luminance values of the foreground and background can be adjusted.
High resolution bitmap mode x graphics produces NTSC artifacts which are "tinted" depending on the color values; it was normally impossible to get color with this mode on PAL machines. For text modes, the character set is easily redirected by changing a register, allowing the user to create custom character sets. Depending on the text mode used the character set can occur on any 1K or byte page boundary in the 64K address space.
Fast and efficient animation can be achieved by simply changing the register to point to different character sets. ANTIC includes additional register controls over character display that permit it to invert flip upside down the character matrix. A register control can also modify the state of reverse video characters which can be used to produce blinking text.
It is the successor to the TIA chip used in the Atari It also provides timers, a random number generator for generating acoustic noise as well as random numbers , and maskable interrupts. POKEY has four semi-independent audio channels, each with its own frequency, noise and volume control.
Each 8-bit channel has its own audio control register which select the noise content and volume. For higher sound frequency resolution quality , two of the audio channels can be combined for more accurate sound frequency can be defined with bit value instead of usual 8-bit. Later PAL versions have the C processor.
Antic Magazine Collection