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1200xl mods


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#26 Rybags ONLINE  

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Posted Sun Feb 26, 2012 2:00 AM

Board space aside, a worthwhile upgrade could have been (minimalist thinking here, maximize compatability) :

- 256 colours globally available.
- Independant fore/background colours in hires modes. e.g. if an upgraded chip was released with the XEs, they could run it at 7 or 14 MHz which would be fast enough for changing colour at 320 resolution.

Having Antic/GTIA seperate didn't really impede what the overall system could do, but we have the ANx bus and GTIA also having to monitor the /Halt line to know when PMG fetches are due.

If they'd been on the one die from the outset, a lot of the real estate for that interface and "prediction" of PM fetches wouldn't have been needed and could have gone towards other functions. More palette entries being yet another on the wish list.

Edited by Rybags, Sun Feb 26, 2012 2:01 AM.


#27 peteym5 OFFLINE  

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Posted Sun Feb 26, 2012 9:52 AM

From the articles I was reading, the combined Antic/GTIA (CGIA) was in development before the 600XL/800XL, would have gone into the XL series first. Atari started shifting back to video gaming around 83/84 before Tremial came in and halted home computer development. By the time of the XEs, no one was willing to further invest in improving technology running with a 6502. 80x86 and 68000 CPUs running at much higher speeds and directly accessing more ram. I know about 65816 but believe it still fell short of what the other CPUs could do. By the mid 1980s, the IBM PC compatible market started to grow because it was the primary computer for business applications, more people wanted a PC. Atari and Commodore had major management issues, but the final nail in the coffin was the VGA and Sound Blaster cards for the PC. By the end of the decade, I don't see how Atari or Commodore could have kept going with a different micro computer platform. Its not just the computers ability to run a video game, its Operating Systems and application software available for it. How many word processors, database and spreadsheet programs are available for the PC?

#28 Gunstar OFFLINE  

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Posted Sun Feb 26, 2012 10:02 AM

How many word processors, database and spreadsheet programs are available for the PC?


And I say, how many do you need?

In any case, business and home computing were destined to merge, and it would be whomever won the business market that would become the eventual standard, plenty of programs would have been around for todays "PC" regardless of which company(s) came out on top. IBM had been an established business name for decades before PC's with main-frames, terminals and type-writers. A Juggernaut.

#29 bob1200xl OFFLINE  

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Posted Sun Feb 26, 2012 10:44 AM

I don't even jumper the CHROMA line - just use composite for CHROMA.

Bob



RetroBits is the newest version of ClearPic, if I remember correctly... The whole video thing is poorly defined, really. What looks good for one is full of birdies for another. I just do the three - jumper mod on my machines. (R63, L15, C115)

Bob


Really! I'm surprised there's that much difference just jumpering those three. The last video mod I did on the 1200XL was SuperVideo 2.1 back in '93 or whatever it was. That one took a bit o' time. Especially since I didn't have a good solder sucker back then. But the result was very good, and still looks great today. I bought a new 1200XL recently, and wanted to try out one of the simpler mods before diving into SV 2.1. Should be easy enough to jumper those three (and hook up the chroma line), then stop and check it out before deciding whether to proceed. Thanks for the tip!



#30 Havok69 OFFLINE  

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Posted Sun Feb 26, 2012 11:06 AM

I ended up doing the retrobits clearpic mod, and it came out great....

YMMV

#31 Ransom OFFLINE  

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Posted Sun Feb 26, 2012 3:33 PM

I did the three-jumper mod along with adding the separate chroma line. It looks nice and sharp on standard def LCD, but on my HDTV it looks blurry. I'm considering removing the RF modulator as my next step (since I'll want that spot for the RGB connector for the VBXE). Is there a doc somewhere that shows what I'd have to add after I remove it?

Edited to add: Never mind, I found the post on adding the wire between shield ground and DC return (thanks, Bob1200XL!).

Will removing the RF modulator leave everything else intact (composite, luma, chroma)?

#32 Gunstar OFFLINE  

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Posted Sun Feb 26, 2012 4:52 PM

yeah, just remove the modulator and add the ground wire and you are good to go!

#33 Ransom OFFLINE  

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Posted Sun Feb 26, 2012 7:23 PM

Cool! I'll get right on that. :)

#34 Ransom OFFLINE  

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Posted Sun Feb 26, 2012 8:50 PM

I just can't get that RF modulator off the board. Of course it's acting as a big heat sink, preventing me from desoldering those four pins. But there's obviously a way to do it. What am I missing?

#35 Stephen OFFLINE  

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Posted Sun Feb 26, 2012 9:00 PM

I just can't get that RF modulator off the board. Of course it's acting as a big heat sink, preventing me from desoldering those four pins. But there's obviously a way to do it. What am I missing?

Large ass soldering gun - 65W to 100W range. Equally large ass solder wick. Lots of patience and VERY FINE control of amount of heat added to the board. Do it in stages. Did a mention copious amounts of patience? Never never force shit, or pry on it, even with a fingernail. Use lots of flux, remove bits of the solder pools in stages. You'll eventually get it all removed, at which time you can heat and bend the tabs straight. Then the modulator will fall out.

#36 Ransom OFFLINE  

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Posted Sun Feb 26, 2012 9:07 PM

Large ass soldering gun - 65W to 100W range. Equally large ass solder wick. Lots of patience and VERY FINE control of amount of heat added to the board. Do it in stages. Did a mention copious amounts of patience? Never never force shit, or pry on it, even with a fingernail. Use lots of flux, remove bits of the solder pools in stages. You'll eventually get it all removed, at which time you can heat and bend the tabs straight. Then the modulator will fall out.


Hmmm. Well, I'll try that next time. Actually, that's what I was trying for quite some time, but I wasn't succeeding. I probably just don't have the patience or the necessary skill. I ended up using this method I found in another thread, posted by Bob1200XL:

To pull a modulator, I just 'cam' it out. You slide a small screwdriver tip under the base, near a solder lug, heat the lug with a good-sized (40 watt) iron and force the board away from the lug and let it solidify again. You are basically bending the PCB, so take it in very small steps, starting at the edge of the PCB. Work your way around the different lugs, prying carefully. After 6 or 8 cycles, the modulator will be free.


Thankfully, it worked and everything seems to be fine. I'll run some tests on it some other day, but for now it plays Centipede OK. So I'm hopeful that I didn't screw anything up.

#37 AtariGeezer OFFLINE  

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Posted Sun Feb 26, 2012 9:41 PM

I just can't get that RF modulator off the board. Of course it's acting as a big heat sink, preventing me from desoldering those four pins. But there's obviously a way to do it. What am I missing?


I just used a 25w iron applying fresh solder and flux and using a small screwdriver to pry it up gently.
Caution: don't try to pry up with too much force or you'll damage the solder pads...

Jay

#38 Gunstar OFFLINE  

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Posted Sun Feb 26, 2012 9:45 PM

I think he's already finished now. I used a 45w desoldering iron I got at Radio Shack for $12. I enjoy using it so much more than tons of flux and braid.

#39 peteym5 OFFLINE  

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Posted Mon Feb 27, 2012 7:24 AM

Board space aside, a worthwhile upgrade could have been (minimalist thinking here, maximize compatability) :

- 256 colours globally available.
- Independant fore/background colours in hires modes. e.g. if an upgraded chip was released with the XEs, they could run it at 7 or 14 MHz which would be fast enough for changing colour at 320 resolution.

Having Antic/GTIA seperate didn't really impede what the overall system could do, but we have the ANx bus and GTIA also having to monitor the /Halt line to know when PMG fetches are due.

If they'd been on the one die from the outset, a lot of the real estate for that interface and "prediction" of PM fetches wouldn't have been needed and could have gone towards other functions. More palette entries being yet another on the wish list.


That was more or less my point. With Antic/GTIA combined, what was the GTIA part wouldn't need an external bus and halt to get data from Antic. Reducing some of the CPU halts probably won't make a noticeable difference, maybe get one or two extra color change within a DLI before the scan line reaches the left side of screen. What would have made a difference is running at 7+ MHz or more. However the major thing is cutting down cost and leaving more space on the board.

#40 Rybags ONLINE  

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Posted Mon Feb 27, 2012 7:43 AM

The CPU halts would still be the same, PM DMA doesn't waste cycles doing anything twice.

What they could have done though - by the mid 80s, the RAM could get by with less refresh cycles, e.g. C64 and Plus4 I believe only use 5 cycles per scanline instead of 9, so a switchable low refresh mode could have sped up the system slightly.

#41 Ransom OFFLINE  

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Posted Mon Feb 27, 2012 7:48 AM

I think he's already finished now. I used a 45w desoldering iron I got at Radio Shack for $12. I enjoy using it so much more than tons of flux and braid.


Those are great. I have one of those, too, and was using it but without success. I have no problems using it with normal components, but I'd never desoldered something so big before. It just wasn't clearing the holes at all. I got the blobs off the top with it, but the holes weren't clearing. I tried solder braid, but that was taking forever. Finally, heating the solder up with a hot iron and carefully and slowly prying the box up, leg by leg, worked.

#42 Rybags ONLINE  

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Posted Mon Feb 27, 2012 7:56 AM

There's an old expression "Less is more".

We can turn it around to "More is less".

Rather than risk ruining vias or lifting traces by trying to coax the last bit of solder from a hole, just add a blob of fresh solder such that you can conduct the heat to the residual stuck stuff. Using enough should mean you contact the via directly with the iron for the least time possible. Then just suck the lot out in one go with the sucker tool.

#43 Ransom OFFLINE  

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Posted Mon Feb 27, 2012 8:04 AM

There's an old expression "Less is more".

We can turn it around to "More is less".

Rather than risk ruining vias or lifting traces by trying to coax the last bit of solder from a hole, just add a blob of fresh solder such that you can conduct the heat to the residual stuck stuff. Using enough should mean you contact the via directly with the iron for the least time possible. Then just suck the lot out in one go with the sucker tool.


Thank you for that tip! I'll keep that in my tips file for next time I run into that sort of situation. I was assuming the RF box was acting as a big ol' heat sink and thus the solder wasn't melting, but of course that wasn't true or I wouldn't have been able to pry it up after heating the solder. So you must be right that I wasn't getting good conduction and perhaps not good suction when it came to the solder further in.

#44 Rybags ONLINE  

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Posted Mon Feb 27, 2012 8:22 AM

Oh... RF box. I thought you were just talking a standard via from an IC.

I had to take the RF box out and reinstall in one of my 7800s. Tabs + big blobs of solder, I took care of that one with a big flat blade iron.

I had one stubborn via where the remnamts of solder and crud were recessed, got that out with a specialist drill that I got as part of a set of PCB drills.
About $23 for around 6 small drills, but well worth the spend.

#45 Ransom OFFLINE  

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Posted Mon Feb 27, 2012 8:37 AM

Ooh...specialized tools. I love specialized tools. :)

#46 Gunstar OFFLINE  

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Posted Mon Feb 27, 2012 10:23 AM


I think he's already finished now. I used a 45w desoldering iron I got at Radio Shack for $12. I enjoy using it so much more than tons of flux and braid.


Those are great. I have one of those, too, and was using it but without success. I have no problems using it with normal components, but I'd never desoldered something so big before. It just wasn't clearing the holes at all. I got the blobs off the top with it, but the holes weren't clearing. I tried solder braid, but that was taking forever. Finally, heating the solder up with a hot iron and carefully and slowly prying the box up, leg by leg, worked.


Yeah, it wasn't like I zipped through it, it still took many times on each leg, and I added flux to help.

#47 Ransom OFFLINE  

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Posted Mon Feb 27, 2012 10:29 AM

Ah...flux! Another idea for me to jot down. Thanks!

#48 Gandor OFFLINE  

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Posted Sat Jun 30, 2012 9:35 AM

Before installing the Ultimate1MB I was thinking of removing the RF modulator and doing the ClearPic 2002 mod.
Since I'm not an electronics expert I have some question regarding the ClearPic 2002 mod which I hope somebody can answer:
1) How many Watt should the resistors be? (My local Fry's has 1/4, 1/2 and 1 W versions)
2) Can different Watt resistors be mixed? (I noticed they only have 2 1/4 W and 2 1/2 W 1 Ohm resistors)
3) What type (Electrolytic or Ceramic) of Capacitors should I get?

Thanks

#49 bob1200xl OFFLINE  

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Posted Sat Jun 30, 2012 11:57 AM

1/4 watt resistors are fine. You may find jumpers ( 0 ohm resistors) that you can use rather than 1 ohm parts or just use insulated wire.

You can mix wattages as long as it fits on the board.

Ceramic capacitors - 25 volts or more.

Bob

#50 Gandor OFFLINE  

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Posted Sat Jun 30, 2012 12:55 PM

1/4 watt resistors are fine. You may find jumpers ( 0 ohm resistors) that you can use rather than 1 ohm parts or just use insulated wire.

You can mix wattages as long as it fits on the board.

Ceramic capacitors - 25 volts or more.

Bob

Awesome, thanks Bob.




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