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Everything posted by shoestring

  1. I haven't had much luck identifying bad DRAMs using the piggyback, I've had some success identifying bad SRAM ( 2114s, 2128/6116 ) with that method. The mT DRAMs I've dealt with have mostly shit themselves to the point where the chip is completely dead or the outputs are floating, I haven't really seen any other failure modes beyond that with these ones.
  2. Galaga, being a fast shooter really needs rot90 monitor orientation ( screen rotated vertically ) to make allowance for distance between player and enemies.
  3. Untitled.mpg Spent a couple of hours on it tonight and it's looking slightly better albeit many bugs. Rather than doing them by hand, the bit patterns in the tiles are now horizontally flipped during initialisation. Haven't implemented any DLIs yet, so excuse the jerkiness. Have some ideas to deal with the vertical stripes in all the graphics.
  4. Here's a very early Dino Eggs WIP I just started a couple of weeks ago. Disassembled original code and working with source derived from that. Yes it needs quite a lot of work! But essentially the Atari is running the Apple II code in an 130xe config. I'm using xbios to load all the original images from the Apple II straight into the available memory banks. At least the bottom row is showing up correctly, looks as though I'm on the right track in terms of using a lookup table to mimic the Apple IIs weird display layout. video.avi
  5. Well, I apologise if it looks as though I'm trying to derail a thread but I also felt the issues were somewhat related and could help someone else out. I've been literally pulling my hair out trying to find a cause. Just an important note before you read on, both ANTICs are C012296D-01 ( replacement and original ). Here is the original. With the replacement, the pmg issue was still present but only for a few seconds and completely disappears as the machine warms up ( maximum 10 seconds, average 5 seconds ). I can definitely live with that. I'm no expert but I don't believe my ANTICs are faulty, there are just some subtle variances where the issue may be exhibited. I had the machine running for hours on end with the old ANTIC and the problem was permanent. Unlike the replacement, the issue does not return as long as the machine isn't powered off for a significant amount of time then powered back on. vid.mp4 Edit: Also, I forgot to mention that there was some PMG glitching at the left and right hand side of display when the screen saver kicked in. It's completely gone now with the new ANTIC.
  6. Like this. It's not present in the loader screen though, at least not for me. So I temporarily replaced the GTIA with a PAL version and thought I'd found the culprit. The replacement GTIA came but didn't help. I do have a spare ANTIC to try sometime tomorrow. Thanks for the heads up.
  7. Could be the 4050 hex buffer. These are CMOS and easily damaged
  8. Never worked on late 80s c64 PCBs, have worked on several from 83 and they are built well. You would have to be fairly careless or inexperienced to lift a trace. The 130xe board that I have was probably one of the easiest I've ever worked on in terms of how quick it took to remove all the chips and socket them.
  9. I think the quality is quite good on all Atari 8 bit PCBs, even the XE. But then again, I'm comparing those against the quality found in arcade pcbs I've worked on from the same era which are horrendous.
  10. I've done the mod on a 600xl, yes the instructions are a bit confusing. It's an NPN transistor, so the emitter is pin 1 on the 2n2222 I can provide some gut shots of the machine as soon as I get home if that helps.
  11. The stock video output should be miles better than the one produced by a 130xe.
  12. It's not an early Apple II revision machine for hoarding purposes. And they produced a lot more of these, they are not going to a few hundred thousand dollars anytime soon.
  13. Yes. This after replacing the dead RAM in my non enhanced IIe with the original mask roms.
  14. This was the power supply that came with my machine. If you got one of these then you were one of the lucky ones.
  15. The IIe will be more useful especially if it's the enhanced version which has compatibility with the IIc. IIe can easily be upgraded to enhanced specs ( new roms and 65c02 ). It's a no brainer really, the IIe should have an 80 col card. That will give you a total of 128kb to play with vs 48k in the II plus. I think the IIe is more reliable as well, less chips, much less that can go wrong which makes them simple to troubleshoot and repair.
  16. Hi. On the look out for a GTIA to replace the faulty one inside my 800. if anyone has any and are willing to ship to Australia then please send a pm.
  17. Bil Herd said that the C64 was designed to be the Atari killer, this is what they set out to do when they drew up plans to build the next machine after the Vic-20.Andy Finkel said that they looked at certain features in the 800 that they liked. In many ways, there’s similarities and similar compromises. Certainly, purchasing MOS really helped make those machines affordable and sell more of them but the war was predominately against TI and Atari just got dragged in to it. Tramiel never forgave TI for what they did to him and as ruthless as he was, he went for the jugular when Commodore’s engineers passed on info that TI were losing money on their CPU, Jack then slashed the prices of all their peripherals by half, then offered a deal to existing TI owners that they’d receive $100 off their c64 purchase if they traded in their machines, forcing TI out of the 8 bit market. Commodore ended up with a lot of TIs in their warehouses, I wonder what they did with them. By 1984, Atari was losing 2 million dollars a day so I don’t think the 1400 and 1450xld would have been produced in enough quantities to gain significant market share regardless of who would have bought the company, those were expensive machines to manufacture and computer manufacturers only have a finite inventory of components they prefer to use on products they can move faster. If Atari ended up with the Amiga, they would not have had the money by that stage to turn those suitcase sized bread boards into silicon.. hence Jack willingly selling the chips to Commodore. Converting those bread boards really took a monumental effort, money and research with the help of people at the Amiga group and CSG aka MOS.
  18. That's damn impressive. I can imagine how much prettier this could be on an Amstrad CPC 6128 with its nice colour palette.
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