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EspañolGEORGE'S TELEVISION INTERFACE ADAPTER
The 'Color Television Interface Adapter' ('CTIA') is the graphics chip used in some early Atari 400/800 home computers. The chip is the successor to the TIA chip used in the Atari 2600.
CTIA was replaced by 'George's Television Interface Adapter' ('GTIA') in later revisions of the 400 and 800, and in all subsequent members of the Atari 8-bit family. No CTIA-equipped Ataris were shipped to Europe. By 1981, all Atari computers were equipped with the GTIA chip. The GTIA chip was also used in the Atari 5200.
According to Joe Decuir, George McLeod designed the CTIA (Colleen TIA) in 1977. Later he also designed GTIA.
The GTIA chip added the following capabilities to the existing CTIA:
★ 256 colors instead of 128. This was done by increasing the valid luminance values from 8 to 16.
★ 3 additional graphics modes. All 3 modes are 80x192 pixels, with the difference being in the colors allowed -- one mode allows for 16 shades of a single hue, one allows for 16 hues with a single shade/luminance value, and the last one allows for 9 colors of any hue/luminance.
GTIA also generates keyboard clicks.
In addition, due to differences in how the CTIA and the GTIA interface with the television, programs that depend on color artifacts will display differently.
Atari owners can determine if their machine is equipped with the CTIA or GTIA by executing the following BASIC command:
: ''POKE 623,64''
If the screen blackens after execution, the machine is equipped with the new GTIA chip. If it stays blue, the machine has a CTIA chip instead.
''by part number''
★ C014805 — NTSC. ''North America NTSC''.
★ C014889 — PAL. ''European PAL''.
★ C020120 — FGTIA. ''French SECAM video''.
★ C020577 — CGIA. ''Combined ANTIC and GTIA''.
Atari 'XE' computers made for the Eastern European market were built in China. Many if not all have a buggy PAL GTIA chip. The luma values in Gr.9 and higher are at fault, appearing as stripes. The only solution is to replace the chip.
★ ANTIC
★ De Re Atari by Chris Crawford
★ Mapping the Atari, Revised Edition by Ian Chadwick
★ GTIA Chip data sheet
★ CGIA Chip data sheet
★ jindroush site(archived) GTIA info
CTIA was replaced by 'George's Television Interface Adapter' ('GTIA') in later revisions of the 400 and 800, and in all subsequent members of the Atari 8-bit family. No CTIA-equipped Ataris were shipped to Europe. By 1981, all Atari computers were equipped with the GTIA chip. The GTIA chip was also used in the Atari 5200.
According to Joe Decuir, George McLeod designed the CTIA (Colleen TIA) in 1977. Later he also designed GTIA.
| Contents |
| GTIA enhancements over CTIA |
| Versions |
| Bugs |
| See also |
| External links |
GTIA enhancements over CTIA
The GTIA chip added the following capabilities to the existing CTIA:
★ 256 colors instead of 128. This was done by increasing the valid luminance values from 8 to 16.
★ 3 additional graphics modes. All 3 modes are 80x192 pixels, with the difference being in the colors allowed -- one mode allows for 16 shades of a single hue, one allows for 16 hues with a single shade/luminance value, and the last one allows for 9 colors of any hue/luminance.
GTIA also generates keyboard clicks.
In addition, due to differences in how the CTIA and the GTIA interface with the television, programs that depend on color artifacts will display differently.
Atari owners can determine if their machine is equipped with the CTIA or GTIA by executing the following BASIC command:
: ''POKE 623,64''
If the screen blackens after execution, the machine is equipped with the new GTIA chip. If it stays blue, the machine has a CTIA chip instead.
Versions
''by part number''
★ C014805 — NTSC. ''North America NTSC''.
★ C014889 — PAL. ''European PAL''.
★ C020120 — FGTIA. ''French SECAM video''.
★ C020577 — CGIA. ''Combined ANTIC and GTIA''.
Bugs
Atari 'XE' computers made for the Eastern European market were built in China. Many if not all have a buggy PAL GTIA chip. The luma values in Gr.9 and higher are at fault, appearing as stripes. The only solution is to replace the chip.
See also
★ ANTIC
External links
★ De Re Atari by Chris Crawford
★ Mapping the Atari, Revised Edition by Ian Chadwick
★ GTIA Chip data sheet
★ CGIA Chip data sheet
★ jindroush site(archived) GTIA info
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