identify AT&T chips

AT&T

20C408
20C409
20C490 (15/16/24 bit, 6/8 bit DAC)
20C491 (15/16/24 bit, 6/8 bit DAC w/ gamma correction)
20C492 (15/16/18 bit, 6bit DAC w/ gamma correction)
20C493 (15/16/18 bit, 6bit DAC)
20C497 (24bit)
20C498 (24bit, 16bit pixel bus)
21C498 (24bit, 16bit pixel bus)
22C498 (24bit, 16bit pixel bus)
20C499
20C505
21C505