ClausB
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Posts posted by ClausB
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Would something like a really small capacitor value on the luma output help with this?Or maybe stronger (smaller) pull-up resistors on the GTIA luma pins? Something for the video mod designers among us to ponder.
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My 80 column system owes a lot to the excellent ACE-80....Thanks! I'm glad to contribute a little bit to the fine job you're doing. Back in the day I modified Letter Perfect to work with ACE-80 but it was not optimal. What you're doing should be the final word (pun intended).
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Normal, yes. Desirable, not really.Back in the day, we were not spoiled by crisp VGA displays, so it was a small minus next to a huge list of Atari plusses.
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Has anyone else seen anything like this on their machine, or is it me that has ended up with a faulty HW?I've seen it on my Ataris. I think it's normal.
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I've been thinking that the core 80 column code from LW could be modified into a high speed generic 80 column driver, patched into E: ...That's what ACE-80 is.
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Ok I got it removed and it works perfectly.You're welcome.
So, you bought the whole thing for $11 and you're selling part of it for $35? Nice.
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I have spent some time looking for the original Byte article, of course to no avail, just to see what was said about ramdisks way back when.Here's the last section of the article - about the RAMdisk software.
Just noticed that I never posted the whole article, so here it is.
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The Whiztronics is a copy of my 1985 upgrade posted here:
http://www.atariage.com/forums/index.php?s...t&p=1481893
Maybe this schematic can help you undo the mod. You can definitely leave the DRAM chips in there. Put the 74LS158 chip back into the U27 socket. If the upgrade was done properly, no traces would have been cut. You should reconnect the 3K ohm resistor at R32 (between +5V and pin 1 of the DRAMs). Good luck.
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Looks very nice!
I'm struggling to speed the thing up....In ACE-80 I sped up scrolling by rearranging the display list instead of moving GR.8 data around. Feel free to borrow the technique or any posted code. See:
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Update! "Our" Tron animation works with OS-b and 48k of memory too (NTSC is also possible)!Nice.
RLL compression or something more fancy?
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Very nice! It runs OK here in Atari++ 1.30 in both NTSC and PAL modes.
Merry Christmas!
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Hmm,Looks like someone took my snow DLI routine and added a utility to change the bitmap and text. He took an early version, though, which has poor timing in switching the background color at the bottom.maybe you can correct this bug ?!? Meaning in the *.OBJ files and maybe also in the *.BAS file if the buggy snow DLI routine is in there ?!? It should be very easy then to add any other Gr. 15 Koala or Micropainter picture and thus to create some more demos in this style...
OK, I fixed it in 2 of the .OBJ files (FROSTY and CHRSTREE). I also changed SNOWFALL.BAS but did not test it. Would you test it?
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I searched for the similar demos I was talking about in another topic some time ago - and found them !LOL! I especially like the Hoseheads. Take off, eh? (Funny 'cause I just got back from business in Quebec - but they don't say "eh" there.)
Looks like someone took my snow DLI routine and added a utility to change the bitmap and text. He took an early version, though, which has poor timing in switching the background color at the bottom.
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Good work! Thanks for posting it.
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So much for that theory!
How'bout this one: luma bits turn off faster than they turn on? The GTIA luma outputs appear to be open-collector because they have pull-up resistors, so this theory makes sense.
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Notice that the worst artifact is between luma values 7 and 8, where all 4 luma bits change. Apparently the lower bits change faster than the upper bits, so the luma goes darker before it gets lighter. The effect is less noticable between lumas 3 and 4 and between 11 and 12, where only 3 bits change. To test this explanation, plot the bars in reverse order and see if the artifacts are light instead of dark.
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This prototype is dated January, 1979 but has parts dated 1978. It also has the yellow-brown rainbow logo.
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Artifacting is....Wow! Very nice explanation without getting into the deep math of color subcarriers, phase encoding, frequency interleaving, and such.
The Atari has 15 hues and 15 lumas in GTIA mode. For each hue, a little chroma pixel appears, that is 1/16th of a color pixel thus:xxxxxxxxxxxxxxxx ---> white pixel
--0------------------- ----> hue 3
--------o------------- ----> another different hue
One thing I've noted is that the size of these varies somewhat.
Really? I always thought that the chroma signal had 50% duty cycle, that is, the "chroma pixels" were 1/2 of a "color pixel", and that only the phase varied with hue.
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Are tech specs available? Memory map, banking schemes, register definitions, etc.?
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If you're wanting less than a full byte, you'll get more random results using the high bits of $D20A rather than the lowWhy is that?
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Hopefully my little experiment may be of help to others who want to make a ver. C cart, and have some of those expensive 68764 or 68766 chips sitting around.Good work! A much cleaner solution than building an adaptor circuit.
I remember the MCM68764 from the mid-80's, when it cost about $40!
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What is the best 320XE memory upgrade?
in Atari 8-Bit Computers
Posted
It's really the RAM test programs themselves that "cause" the behavior. Those upgrades existed in 1985 and the test programs came later. So, the test programs failed to work properly with existing upgrades.
My original 256K upgrade instructions explain clearly that there are only 12 16K banks of extended RAM. Just because there are 4 bank-select bits does not mean there have to be 16 valid values. The Atari chipset itself has some hardware registers where not every bit combination is a valid one. Also, the 4 "invalid" banks are really just copies of the base RAM. That in itself can be useful, especially the copy of the RAM under the OS.
So, upgrades that add RAM are not superior. One could even argue that they are inferior because they have more RAM chips and circuitry that could go bad.