Inside Atari

Atari 1200XL - the New Computer

by Levon Mitchell

The newest ATARI computer, the sleek 1200XL, has made its appearance at the head of the family line. It can be used directly as a general-purpose 64K computer, or, with its new Operating System, as an upgrade to the ATARI system of hardware and software, with which it is compatible. The 1200 also offers several new features and suggests developments yet to come.

Improvements in color and sound output are probably the most notable. New chrome circuitry steps up color saturation 100% over the 400 and 800 computers. The sound capability of the POKEY chip is enhanced by the increased audio-amplifier bandwidth. There are several new special-function keys, a HELP key, a set of international characters, and a completely redefinable keyboard.

Appearance

The 1200XL is much trimmer than its siblings, and has no doors or lids. The single cartridge slot is tucked away on the left, along with two controller ports. Ports 3 and 4 have been eliminated to allow OS flexibility, and the RF wire leading to the TV is detachable from the computer, if desired. Other connectors are the same as for the 800. The function keys have been moved to the top of the keyboard and include five new ones. The inverse video key (formerly Atari logo) has been moved to the functionkey row, which will please touch typists who were bothered by its position on the older keyboards.

The Operating System

A new 14K Operating System replaces the old 10K OS used by the 400/800. It supports all the legal operations of its forerunners, corrects a few known problems in these, and takes on some new roles. Most important is a fully redefinable keyboard. This gives the astute programmer 174 new keys (including SHIFT and CTRL) to work with. The familiar set of ATARI graphics characters remains available.

The OS provides self-checking on power-up. The new HELP key allows the user to test RAM, ROM, Video and Sound output manually. The other new function keys do the following: one turns off the video display (ANTIC), allowing the user's program to run substantially faster; one disables the keyboard (permitting the computer to be used for control or display purposes without accidental or malicious interruption); another disables the audible "clicks" echoing keystrokes; and the last substitutes an international character set of 29 letters (often used in non-English alphabets) for the standard graphics set. Cartridges can be inserted and removed while the machine is running, without damage to either the machine or the cartridge.

Four ANTIC modes (4, 5, 12 and 14), previously inaccessible except to the Assembly Language programmers, are supported by the new OS and will appear as additional Graphics Modes in the language cartridges. It is also now possible to program certain changes in machine parameters. For example, the automatic key-repeat rate can be speeded up or slowed down.

There are other enhancements only advanced programmers will appreciate. Some of these are: printer unit numbers in the IOCB allowing up to eight printers to be designated; display-handler improvements; and end-of-line automatically appended to the printer-handler buffer.

Hardware

The architecture of the 1200XL is similar to the 400/800. ANTIC, GTIA, POKEY and PIA are the same. The 6502 microprocessor, however, is not the same as in the 400/800. It has been improved with onboard logic drivers and the addition of a HALT line. The new machine allows the user to disable the OS and use 62K of RAM simply by toggling a bit in the PIA. However, if the ANTIC, POKEY or GTIA chips are to be used without the Operating System, the user must provide all housekeeping for the chips. There are no parallel-bus output or test points accessible to the user.

Sound-Color

The improvements in color and sound with the 1200, in my opinion, are substantially ahead of other machines in the crowded marketplace of home computers. The designers aimed for equivalence to broadcast-TV color levels, and achieved a 2:1 color saturation improvement over the 400/800. The problem of color bleeding, or overlapping, occasionally seen on the 800, has been reduced by the new circuitry.

Atari has improved the design of the sound processor (POKEY) to produce the widest frequency response available on personal computers today.

Simplicity

All of the electronics for the 1200XL are on a single printed circuit board. The obvious advantage here is the improved reliability. There are no mote insertion problems, bad connectors, or corrosion to worry about.

Three new hardware peripherals designed to match the 1200XL are also included by Atari. These are the 1010 Program Recorder, the 1025 80 column Printer, and the innovative 1020 40-column Printer/Plotter, all of which are compatible with the ATARI 400 and 800 home computers.

The 1200XL is close to being the "super system" some might be expecting. I think it is as much ahead of the competition as the 800 was in 1979. Atari has plans for a full line of new peripherals and software for the 1200 -disk drives, printers, modems, voice synthesizers, etc. I think the Atari community will be pleased with the 1200, and that it is an attractive tool for the serious programmer.

Levon Mitchell has been in the computer field for more than ten years, the last three with Atari, where he has worked on various projects for the Consumer Electronics Division and the Home Computer Division. He is now with the Special Projects Group at Atari. This material was written with the cooperation and approval of Atari, Inc.