knnngt@ukma.UUCP (Alan Kennington) (02/23/86)
In article <709@ihwpt.UUCP> knudsen@ihwpt.UUCP (mike knudsen) writes: >I took a closer look at the pretty colored Atari flyer >spec sheet, and not only is the vertical frequency >up to 71 Hz, but the Horizontal is a whopping >35.7 KHz, or 2.13 times the NTSC standard 15.75! > >This answers a long-standing question-- >ST Monochrome is NON-INTERLACED! >It really draws all 400 lines in each of 70 frames/sec! >Atari really went all the way on this. > mike k > >PS: This assumes that the spec sheet is correct. Here's a simple test for checking whether a monitor is interlaced: First you display a blank screen - i.e. all white. And you wave your finger in front of it. Do it fast enough to make 8 images of your finger appear on the screen. Now get a stop watch and time 40 waves of your finger - i.e. 640 images of your finger altogether. I did this and obtained 640 images in 8.96 seconds. This gives 71.43 Hz as the image frequency. I know this is just luck that it is so close, but an accuracy of only about 20% is necessary here. Second, you display only every odd or even line, which should give a frequency of half as much for interlaced, or the same for non-interlaced. I just tried the same test on the GEM desktop dither pattern and got 70.80 Hz. This is not surprising, because the dither pattern uses all lines. Could some good person please do the experiment for alternate lines only. I haven't got my second disk drive in the mail yet. So I can't be bothered to write a C program for it. Alan Kennington.