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Shawn Jefferson

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Shawn Jefferson last won the day on January 5 2011

Shawn Jefferson had the most liked content!

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About Shawn Jefferson

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    River Patroller
  • Birthday 12/22/1973

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    Male
  • Location
    Victoria, Canada
  • Interests
    Atari, Karate, IT Security, vintage gaming, old british cars (MGB)

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  1. Gave it another crack and improved my score slightly!
  2. I think I'll get last place sewn up! 36,845 is my highest so far. Playing on real hardware (600XL with video port added, 64k upgrade and Ultimate 1mb), running through a retrotink to the LCD.
  3. Hi, yes, the 1400XL MMU is different from all the others. It's close, but not quite the same. I have looked into using a GAL, and the TL866 programmer, and that looks like a good option, but without knowing if I have an actually good set of equations (or a dump of the Atari part) I don't think it will help me much. I had someone else program the PAL A and PAL C chips for me (actually two different people just to make sure)!
  4. The system seems quite stable when playing Star Raiders or Star Raiders 2, and I can let the memory test run for a long time with no change. There is another ROM chip, but all those devices in the 1400/1450XL are all PBI devices, so I don't think this ROM comes into it (and least not yet). The more I think about it, the more I am thinking its something to do with the PAL A (MMU) chip that I attempted to program from the equations. It's similar to that in the 1200XL and the 800XL, but not exactly the same. Although it seemed like so much of the machine is working properly, with banking ROMs in and out that it's a bit confusing. Maybe Bob Wooley would dump the PAL A chip like he had done for the PAL C, I'll have to PM him, as he seemed like the only person with the board and the capability to dump it.
  5. Thanks, I found the Atari PDF on Freddie and see it's controlling CAS/RAS generation from address lines. I guess it may still be the issue for me, perhaps. The MMU in the 1400XL is the 61919 (PAL A), that certainly could be the issue since I was not able to source that chip, or get a dump of the official chip, and tried to rebuild it from the original equations (see the thread below). I'm not sure how that could be the issue with the things that are working though? The most likely scenario is that I've screwed up the equations of that PAL A chip somehow, but very strange with the way things are working if that is the case.
  6. I'm using CO61598B, which is the single chip OSROM, and I've swapped it out, it doesn't seem to be a problem with the actual OS ROM, and to get the system to even boot into self-test and diagnostic carts it would have to be working somewhat. I also was able to get SALT2.05 on my Atarimax flashcart and verified that C000 and C0001 have the correct checksum values. I don't see how it could be the OSROM, or the socket, since data bus lines and address bus lines would have to be working just to get this far? I haven't swapped the MMU (freddie) out, since I don't have a spare, and likely any chip in my 130XE or 65XEs would be soldered in, and I'm not sure I want to try desoldering it. I could get another one from Best maybe. Do you think the symptoms I'm seeing here would indicate a problem with MMU? I'm not sure what the Freddie MMU does exactly? PIA I've swapped out and that appears to be working in another machine. I can't test that much in this machine with it only going to self test though. But it does look like portB is working, since I can enable/disable BASIC it appears (self test showing different number of RAM blocks).
  7. The ROM is the standard XL OS production ROM chip, I haven't made any alterations to it (tried two different ROMs).
  8. I found today that Star Raiders II also has the diagnostic bit set, so I can run that as well. Everything there seems to work properly as well, although I haven't played a game yet to see if it's all working. I also checked continuity between the CPU address lines and two LS244 chips (buffering the address lines?), and to the OS ROM, and all were fine.
  9. Hi, I'm troubleshooting my 1450XL build, see thread here: And I'm having an issue where the machine goes straight to self test, and the first ROM square is red. All other ROM and RAM tests are green. As I'm troubleshooting and trying to track down the issue, I need some help in where to look. Here's what I know and am assuming: Holding option will allow the self test to show 48 RAM squares, so banking out BASIC seems to work Star Raiders cartridge works and plays, I can fly around and press keys, etc.. No sound though, might be related or not. I have swapped many chips: OS, BASIC, CPU, GTIA, PIA, no change. Continuity checks here and there, no issues that I can tell (but maybe didn't check everywhere) Looking at the OS disassembly and what it's doing during the self test, it looks like it's doing a checksum over C002-D000 and also 5000-5800. Somehow that is failing, but since self test works, that's being banked in properly anyway (maybe not banked out, as the OS tries to do before the checksum routines, but would that actually cause the OS checksum to fail?), because the OS is partially working, and Star Raiders is working, I think all the data bus lines to the OS ROM are working fine, and probably (?) all the address bus lines. Any ideas where to look next? The PAL chips that help with banking may be wrong, but it appears that everything is being banked appropriately from what I can tell. I don't have a SALT cartridge, which would probably help a little narrow things down... might be my next project to build one. I have a logic probe on the way, but no logic analyzer, might be another purchase soon, lol.
  10. I got impatient and soldered in Y2 where I thought it should go, and I now have signs of life! Unfortunately I still have some problems somewhere. I'm getting a picture, which is good, but it's going straight into memory test and showing the first ROM bar as red. All memory tests pass, and holding down Option shows 48 RAM squares as expected. Star Raiders cartridge works and I can play (although I don't have sound, but one problem at a time!). I've swapped the OS ROM, reseated the BASIC rom, swapped BASIC rom, checked continuity around the OS ROM a little, tried reflowing the pins on the OS ROM.
  11. Going through everything on this board, and I had a question, where does Y2 go? I haven't soldered this on but I have the part X115-ND. Looking at the pictures of completed boards, and it looks like it's "next" to the two large holes besides the Y1 marking, and it fits here, but I'm not sure, all those holes just look like vias. Also, another (probably dumb) question, should I fill all the vias with solder, or just leave them open? Continuity seems ok from all the testing I've done.
  12. Thanks! I can add that to my chip tester now.
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