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Rybags

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Rybags last won the day on September 1 2016

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About Rybags

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  • Birthday 10/01/1967

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  1. I'd be pulling and reseating (or adding socket for) MMU and PIA. Though sort of strange that all those games were OK but a Basic cartridge failed.
  2. CTIA is very rare - supposedly only went into production machines for less than 18 months. Lots of people would have taken the upgrade offer which means even more rare. Detection method - the only thing I can think of besides setting up a mode and prompting the user is PM collisions. Unsure if that'll work. PMs can work a bit differently when GTIA modes are enabled.
  3. OS Rom for CTIA? I don't get that. Supposedly the official OSes for 400/800 are rev A and B for NTSC and only A for PAL. It would be fair to assume an OS-A NTSC machine has CTIA but it's not a given. Plenty of people took up Atari's offer to upgrade to GTIA (from memory you paid for the chip but the official service centres installed it for free) It's been discussed before, and the generally accepted thing is that PAL CTIA probably never existed.
  4. CTIA detection - how does that work? Do you use a GTIA mode and create PM to PF collisions or something?
  5. You don't need to change anything. If you're happy with having the loading pic which then waits for the key or fire button, the RTS should be sufficient to continue the load process. The RC pics seem to have a 2E2-2E3 segment which is an INIT. So if you just append your executable file to the pic executable it should be enough. Not sure if RC allows a set delay also which for a game might be desirable. But you could add it yourself easily enough, like just alter the code there. skp dec timer1 bne skp2 dec timer1+1 beq stop skp2 Before the pic runs you'd need to set word timer1 to some value, e.g. 600 which would be 10 seconds delay for an NTSC machine.
  6. Not sure if there's an option to generate source code with RC. But the executable generated - runs with interrupts disabled, checks for fire button and key presses at the bottom of screen. If one of those conditions met, it enables VBlank and issues an RTS. So, should be suited fine for chaining as an early part of a game. One thing to note, the memory occupied won't be cleared so don't rely on RAM containing zeroes (which really we shouldn't do anyway)
  7. You don't have to open anything. Just start with Basic or Memopad and hold a key down.
  8. The main things that will be different are key repeat and the tables that control tape loading. Supposedly the tapes shouldn't have a problem though as there's meant to be 5% tolerance built into Pokey. If it actually is an NTSC OS though, the key repeat on a PAL system would be annoyingly slow. You should be able to pick it straight away.
  9. Older machines are easy to detect. Bit 0 of PORTB switches the OS in or out. So regardless of version or aftermarket modification that should be a universal indicator. PORTB on XL/XE by default will have all bits in output mode - though in a testing situation you'd probably want to do save/restore and put them in output mode to test the OS switchability.
  10. I'm not sure it was written with the older machines in mind (though should have) But it seems to have found you 've got a PAL Antic and NTSC GTIA. Does that agree with what I suggested to try in your thread about the modded 800?
  11. The audio mix with SIO audio in and the PBI/ECI audio in occurs after Pokey. So, in conjunction with the GTIA CONSOL bit, we have 3 extra audio sources that get added. If that circuit is replaced then obviously those things have to be picked off and added to the new output circuit.
  12. The key repeat rate is hard-coded so if the Antic from another system is present the key repeat will seem wrong. Properly converting any machine NTSC to PAL is usually a non-trivial thing since a proper PAL signal needs the 4.43 MHz crystal and extra circuitry that's usually not present on NTSC machines. ? PEEK(53268) should return 1 for a PAL GTIA, 15 for an NTSC one. Telling which Antic is present isn't quite as easy. In Basic the easiest way might be to just use the frame counter updated in VBlank. 10 POKE 20,0:POKE19,0 20 S=PEEK(20)+PEEK(19)*256 30 POS. 0,0 : ? S/50 ; " " ; 40 GOTO 20 Run that and compare against a watch after about 30 seconds. If it's running apparently too fast then it's got an NTSC Antic.
  13. Those switches tend to get a fair bit of free play in them when aged. They're pretty good quality to begin with and likely there's still off-the-shelf replacements or near matches around.
  14. Have to say that's a pretty good effort for the size of program.
  15. Well the obvious thing now is to throw RC at it (would probably go well with some prep like making the background a uniform luma so colours don't go to waste)
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