DonutCity Posted December 6, 2005 Share Posted December 6, 2005 Ok, maybe a reach here - is there any way to tell if a particular Atari 800 has the older CTIA graphics chip or the later released GTIA chip? (Or better phrased, what's the "easiest" way to tell...) Quote Link to comment Share on other sites More sharing options...
Rybags Posted December 6, 2005 Share Posted December 6, 2005 If it's PAL, 100% on GTIA. Apparently, the early NTSC (1st 18 months?) had CTIA. To find out quickly, POKE 623,64. If nothing happens, it's the old CTIA. I would suspect that the CTIA only had the Rev. A OS, but don't have any info on that. CTIA also has different artifacting for slim lines in high resolution as well. Unknown if you can detect the difference in software. The only way I could think would be to put a PM graphic on a fat pixel and test for a collision. 1 Quote Link to comment Share on other sites More sharing options...
DonutCity Posted December 6, 2005 Author Share Posted December 6, 2005 So majority of the 800's were manufactured with the GTIA chip? Any correlation with the “flip tabs” access to the ROM and RAM cards versus the screwed in access covers? Quote Link to comment Share on other sites More sharing options...
Rybags Posted December 6, 2005 Share Posted December 6, 2005 I would say that if you factored in the XLs and XEs, that over 95% of 8-bit machines have the GTIA. Additional to that, there was an option for owners of older machines to have it retrofitted. I think the screwed in covers came about once the 800 came standard with 48K. In the early days, RAM expansion was in 8K increments, plus the OS was modular in aniticipation of enhancements later on. Quote Link to comment Share on other sites More sharing options...
drac030 Posted December 6, 2005 Share Posted December 6, 2005 Ok, maybe a reach here - is there any way to tell if a particular Atari 800 has the older CTIA graphics chip or the later released GTIA chip? (Or better phrased, what's the "easiest" way to tell...) This program: http://drac030.krap.pl/si209.arc should tell you. Quote Link to comment Share on other sites More sharing options...
Almost Rice Posted December 6, 2005 Share Posted December 6, 2005 (edited) Ok, maybe a reach here - is there any way what's the "easiest" way to tell... 977311[/snapback] 10 GRAPHICS 9 20 GOTO 20 If you get a black screen, you have the newer GTIA chip. If you get a blue screen, you have the older CTIA chip. Of course you would need a BASIC cart. The original source of this info Edited December 6, 2005 by Almost Rice 1 Quote Link to comment Share on other sites More sharing options...
DonutCity Posted December 6, 2005 Author Share Posted December 6, 2005 Cool, excellent find!! Looks like I have the GTIA chip and Revision B of the OS. Helps to put a manufacture date on my machine as well...Thanks... Quote Link to comment Share on other sites More sharing options...
jacobus Posted November 1, 2010 Share Posted November 1, 2010 I want to downgrade a GTIA 400 to CTIA. Do I need anything other than a CTIA chip? I'm assuming I can just swap the chips... Why? ... good question - it's on older 400 that was originally CTIA and a) I'd like to see what the difference is like, b) it would be interesting to restore it to the original condition. thanks! Quote Link to comment Share on other sites More sharing options...
Rybags Posted November 1, 2010 Share Posted November 1, 2010 You shouldn't need anything else. But your problem will be finding a CTIA to begin with. Quote Link to comment Share on other sites More sharing options...
Bryan Posted November 1, 2010 Share Posted November 1, 2010 I'd like to de-cap both a CTIA and GTIA and see if the CTIA is significantly different. I've heard rumors that the CTIA was a stop-gap release because the GTIA modes weren't yet working right. Quote Link to comment Share on other sites More sharing options...
SeaGtGruff Posted November 1, 2010 Share Posted November 1, 2010 As far as I know, the only "advantage" to having a CTIA chip instead of GTIA is that the artifacted colors are nicer. It kind of stinks that some games made use of the CTIA artifacted colors, but they don't look "right" with the GTIA chip. Michael Quote Link to comment Share on other sites More sharing options...
Kr0tki Posted November 1, 2010 Share Posted November 1, 2010 Unknown if you can detect the difference in software. The only way I could think would be to put a PM graphic on a fat pixel and test for a collision. This article describes how to detect GTIA by software. I want to downgrade a GTIA 400 to CTIA. Do I need anything other than a CTIA chip? I'm assuming I can just swap the chips... Why? ... good question - it's on older 400 that was originally CTIA and a) I'd like to see what the difference is like, b) it would be interesting to restore it to the original condition. If you get it working, please share the results. There is a report stating that in CTIA player/missle graphics was not aligned with playfield graphics. I'd like to see how it looks and verify whether it affects detecting collisions between P/M and playfield graphics. I'd like to de-cap both a CTIA and GTIA and see if the CTIA is significantly different. I've heard rumors that the CTIA was a stop-gap release because the GTIA modes weren't yet working right. IMHO it's true. Notice that support for GTIA modes 9, 10 and 11 was already built in OS rev. A, that's before GTIA was released. Quote Link to comment Share on other sites More sharing options...
OldAtarian Posted November 1, 2010 Share Posted November 1, 2010 (edited) Honestly, since most of the A8's ever released came with GTIA and many of those that didn't have long since been upgraded or disposed of, it's not going to be very useful at all. If you were contemplating writing software that requires a CTIA, there's not going to be many people that can use it. Even finding a CTIA to do the downgrade with is going to be challenge as most of them are probably gone by now. You might accidentally stumble on one if you were to start collecting 400's and 800's with low serial numbers, but that may take a long time and could be extremely expensive if you don't find one in your first few buys. Edited November 1, 2010 by OldAtarian Quote Link to comment Share on other sites More sharing options...
jacobus Posted November 11, 2010 Share Posted November 11, 2010 I found a CTIA here but sadly, it looks like I bought the very last one. (I tried Best Electronics as well, but after another crappy customer service experience, I discovered they are out of stock as well) I installed it in my 16K 400, but as that the Acid test requires 48K, I had to move it to an 800. The downgrade appears to be perfectly successful (see picture) The results of the Acid test are here. Not sure what tests to subject it to next (suggestions welcome) Quote Link to comment Share on other sites More sharing options...
Rybags Posted November 11, 2010 Share Posted November 11, 2010 Since you've got a CTIA, we'll need you to settle a myth relating to the PMG positioning. Can you run this in Basic and get a screenshot: 10 GRAPHICS 0:SETCOLOR 2,3,2 20 POKE 704,136:POKE 53248,68 30 POKE 53261,255 40 COLOR 160:PLOT 0,0:DRAWTO 39,20 Quote Link to comment Share on other sites More sharing options...
+orpheuswaking Posted November 11, 2010 Share Posted November 11, 2010 (I tried Best Electronics as well, but after another crappy customer service experience, I discovered they are out of stock as well) That suprises me, Best is usually pretty good at taking care of people Quote Link to comment Share on other sites More sharing options...
jacobus Posted November 11, 2010 Share Posted November 11, 2010 Since you've got a CTIA, we'll need you to settle a myth relating to the PMG positioning. Can you run this in Basic and get a screenshot: 10 GRAPHICS 0:SETCOLOR 2,3,2 20 POKE 704,136:POKE 53248,68 30 POKE 53261,255 40 COLOR 160:PLOT 0,0:DRAWTO 39,20 sorry about the quality - crap-o-matic camera Quote Link to comment Share on other sites More sharing options...
Bryan Posted November 11, 2010 Share Posted November 11, 2010 Hmmm... you're going to need single-pixel resolution to see the difference in position. I'd probably use all gray coloring so the TV doesn't throw any color shadows in there to obscure things. Quote Link to comment Share on other sites More sharing options...
jacobus Posted November 11, 2010 Share Posted November 11, 2010 I did some more testing with my CTIA 800, this time just trying a series of common games. The only problem I noticed (so far) is with Galaxian (the Atari version) which is totally messed up. Just to be sure, I tried it from the same source on a GTIA 800 and it works perfectly. Every second or so, the aliens with 'ears' would return to normal, and the normal ones beside them would grow 'ears'. Back and forth. The player's ship is near the top of the screen (above the horizontal bar) and is subject to collisions. Quote Link to comment Share on other sites More sharing options...
Rybags Posted November 12, 2010 Share Posted November 12, 2010 Could you try that Basic example again except with "SETCOLOR 2,0,0" and "POKE 704,6". Then try typing some text and inverse Spaces around the stripe, then tell us in your judgement if you think the stripe isn't exactly aligned with the character boundary (the inverse spaces should adjoin the edge of the stripe). The reasoning for this is that one document suggests that the PM Graphics were offset by single hires pixel (which I have real doubts about). Probably not worth worrying about a photo - you need just the right lighting conditions for a TV photo to look any good, you usually need to eliminate all external lighting influences. Quote Link to comment Share on other sites More sharing options...
SeaGtGruff Posted November 12, 2010 Share Posted November 12, 2010 Could you try that Basic example again except with "SETCOLOR 2,0,0" and "POKE 704,6". Then try typing some text and inverse Spaces around the stripe, then tell us in your judgement if you think the stripe isn't exactly aligned with the character boundary (the inverse spaces should adjoin the edge of the stripe). The reasoning for this is that one document suggests that the PM Graphics were offset by single hires pixel (which I have real doubts about). Probably not worth worrying about a photo - you need just the right lighting conditions for a TV photo to look any good, you usually need to eliminate all external lighting influences. Based on the photo he already posted, I'd say it looks like there *is* a single hi-res pixel offset. It's hard to say for sure, but it does look like the left edge of a block is peeking out from the PM stripe. Michael Quote Link to comment Share on other sites More sharing options...
Rybags Posted November 12, 2010 Share Posted November 12, 2010 Hard to say. The PM is luma 8 but the text is 10. Higher luma tends to make the pixels swell up on a CRT. Quote Link to comment Share on other sites More sharing options...
ijor Posted November 12, 2010 Share Posted November 12, 2010 There is a report stating that in CTIA player/missle graphics was not aligned with playfield graphics. I'd like to see how it looks and verify whether it affects detecting collisions between P/M and playfield graphics. We talked about this some time ago. IIRC, you were involved in the debate as well. My conclusion was then, that the shift is not exactly between PM and PF, but between high rez and non-high rez (including PM). If I'm correct, it is a shift between chroma and luma, and it is the same shift that provokes the difference in artificats as well. And I think that this probably does not affect collision. Quote Link to comment Share on other sites More sharing options...
phaeron Posted November 12, 2010 Share Posted November 12, 2010 I checked jacobus' Acid800 results again, and if there were a detectable shift between PM and PF graphics, the ANTIC: Character Control test should have failed since it uses the sprites to scan the playfield. This tests both lores modes (4-7) and hires modes (2-3), so the hires collision bits don't appear to be skewed, either. Quote Link to comment Share on other sites More sharing options...
ijor Posted November 12, 2010 Share Posted November 12, 2010 I checked jacobus' Acid800 results again, and if there were a detectable shift ... It makes sense to me, phaeron. I am guessing that the shift is on the signal that in the schematics is called /40CHR (it seems to me that is the name). This is the signal that generates the high-rez graphics. It bypasses collision logic completely, it goes directly to the LUMA output logic. If that is correct, then it shouldn't be detectable by software. Quote Link to comment Share on other sites More sharing options...
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