Anyone that's seen an Atari 400/800 next to a VIC-20 or C64 will know what I'm talking about - the Atari display was much, much sharper. It had a similar advantage over the Apple II, and I seem to recall the CoCo being somewhere between the Atari and C64's.

Does anyone know why? I suspect it might have something to do with all the shielding, which would imply later models in the XL series would lose some of the sharpness, but I did not use those machines either.

  • As here? youtube.com/watch?v=UNf8OQaud2M&t=7m51s That's exactly the same quality the C64 reaches on a TV set. If you wanted better quality, you had to connect a good monitor to both. – Janka Dec 21 '18 at 22:55
  • I have no idea what's going on in that video, but I assure you the normal output of the machines was dramatically better than shown. Dramatically. And that is a monitor. – Maury Markowitz Dec 23 '18 at 0:27
  • The video output of a C64 on a monitor is also not that bad. Not even with composite. The TV modulators Commodore used are crap, yes. – Janka Dec 23 '18 at 0:29
  • This is very interesting. In Germany the "Stiftung Warentest" (an organization testing products of any kind) tested home computers in 1984. The computers tested were: C64, TI-99, 600XL, CoCo, Dragon 32, Spectrum, Color Geny. (PAL versions, not NTSC) Their result was that only C64, Spectrum and TI-99 had a "good" picture on the TV set. 600XL was the only machine with the result "bad picture". – Martin Rosenau Dec 23 '18 at 9:42
  • Well that's why I added the comment about the XLs, these were cost-reduced machines so I'm not surprised if the video was not the same quality. – Maury Markowitz Dec 23 '18 at 16:50

Why did the Atari's have such clear displays?

I suspect it might have something to do with all the shielding

No. As usual it's about the effort the designers did put into the display. To reduce cost, the VIC-II outputs an already internally mixed B&W signal and chroma. While this is basically like S-Video, the quality is defined by the internal generator - and doing analogue on a primary digital process is always a challenging task - especially if one want's to save money like Commodore did. In addition the external circuit is rather frugal.

In contrast the Atari's CTIA/GTIA output is fully digital and gets further 'sharpened' by a 4050 CMOS inverting buffer. Thus these signals are already way more 'clean' before geting mixed in a somewhat more elaborate diskrete analogue section. Here is a nice page showing the circuitry in detail for the purpose of an easy modification to get an S-Video compatible output.

Also the modulator used, at least for the 800 is of a better quality than the one for the C64 - but that's only relevant for TV, which is less than desirable anyway - still, here the Atari outperforms the Commodore as well.

I guess it pays out that Atari designers had quite some experience with TV/colour when creating the 400/800 output circuit.

  • Honestly, the only major difference I can make out is the resistor ladder for the luma not being present in the VIC-II schematic. That makes total sense as the VIC does only employ four levels of luminance – black, dark, light and white. I can't see how this affects signal sharpness. – Janka Dec 22 '18 at 2:17
  • A fine answer as always Raff. I can't speak to the internal signal because I only ever used it on a TV. The Atari's TV output was basically the equivalent quality of the C64 on a 1701. I wonder if that's the reason Atari never released their own monitor, simply that it didn't make enough of a difference? I saw an 800 on a monitor, and it was better, but not a lot better. – Maury Markowitz Dec 23 '18 at 0:26
  • Oh yeah, were you ever able to grab pix of the Sol-20 expansion bus? – Maury Markowitz Dec 23 '18 at 0:31
  • Yes. I totally forgot about them. sorry. Let me search and send them. ok? – Raffzahn Dec 23 '18 at 0:46
  • @MauryMarkowitz Looking at the signal with a scope will show the quite obvious difference. Fro the mintor I guess Atari always thought of home consumers using a TV as their main target market. – Raffzahn Dec 23 '18 at 0:48

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.