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Rybags last won the day on September 1 2016

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  1. Does the peripheral bit-bang? How about if it uses 2 stop bits instead of 1 - would that ensure we don't get overrun due to insufficient cycles, but not lose too much speed?
  2. Couldn't the checksum just be computed at end of frame? Or are we talking IO operations of large chunks where it'd create a big overhead between blocks?
  3. I doubt it. The Pokey design tried to incorporate subsystems to reduce component count, e.g. using the audio system to drive part of the SIO system. I doubt they copied elements of anything except TIA. And a fair chance at the time that MOS wasn't letting much out other than the datasheets to purchasers of their chips.
  4. I suspect any flicker would be due to object reuse and redefining won't be any help there.
  5. Might be normal - you could test by pressing the RESET key after power on (not sure about 1200XL but all other XL/XE OS variants have a software generated delay of a fraction of a second) It generates a Reset signal and given the equipment you have you should be able to interrogate that.
  6. I was going on the premise that the incoming stream would be ready to display by Antic. Of course if processing was required then you'd be lucky to hit 2 FPS.
  7. I never bothered to write a program to initialize the menu. I practically remembered the value to plug into the bitmap and just did that, not sure I even bothered to adjust the free sector count. An alternate way could be to create a 2 sector file on the newly formatted disk then manually set it as deleted in it's VTOC name entry - that would stop overwrite but have the free sector count at a proper value.
  8. I had no idea... possibly time for me to look into aquiring one.
  9. Hex editor? Why? Just delete the files from the disk and put your own on there. Back in the day I used to have to create the initial disk manually though... copied the first 5 sectors then manually adjusted the VTOC bitmap to mark 4-5 in use.
  10. At this point the quickest IO speed involves the CPU moving the data. That method is at least 8 cycles per byte which is too slow for decent video, especially if you want to use programming tricks to get better graphics (ie more colours). Throw in DMA and refresh losses and you're looking at maybe a tad over 150K per second theoretical. Another method, I think phaeron might have used it, could be to just read the data and get Antic to just display from the hardware data buffer. That frees up the CPU somewhat but requires fairly precise timing to get it right. The ideal (maybe) would be to use our non-existent (at this point) device that does DMA transfers rather than relying on the CPU. Or ideal #2 - a coprocessor device in cartridge that reads from SD then presents the data in it's internal RAM to be displayed by Antic. But as for live streaming - more complex and needing a custom external hardware solution. And still, we have possibly great cost for the sake of having video at a crappy resolution and framerate with not very much colour (OK, we might get 80x200 256 colours) and we've not even started to consider audio yet (though that could be just fed as analog into SIO or PBI for nothing)
  11. The delay line is used to generate the partial cycle delay important for Ras/Cas in memory accesses. So a good idea to verify it's operating within specs. Although... if you get that static background colour that doesn't go black it's indicating the OS isn't even getting a start. I'm not sure if it can go bad, but maybe the power on/reset circuit? Also the 74LS138 at U2 - used for memory selection in the IO space.
  12. I doubt your problem is related to the crystals. ~ 4.3 MHz corresponds to the colourburst generation which gets fed to PAL GTIA and isn't used anywhere else. Screen that stays black or occasionally brown or red means the OS isn't starting at all. Other parts you should consider if not yet tried in another machine are the delay line, MMU and PIA. Note that the MMU isn't compatible with 1200XL or XEGS. Of course all that aside there's always the chance it's a passive component or the motherboard such as severed trace or solder joint gone bad.
  13. Top adjustable seems pretty common. In theory you could probably just mount one on the bottom of the board though you'd likely need to embiggen the hole in the shielding, and test for sufficient clearance before starting.
  14. Tried (Sierra OnLine) (US) (a) in Altirra but couldn't replicate any such result - it goes to Self Test without any apparent disk activity. The tragedy of this game - such potential but let down immensely by lack of polish and the infuriating way it has that delay when you lose a life then just plonks you back into the action sometimes 1/4 of a second from an obstacle that makes you die again. Just played it and got to the pond jump guarded by the snake, I don't think I ever got much further than that (though watching a longplay that's almost at the end and I have finished it before) Just noticed - the C64 version has a nice title screen bitmap that might lend well to a G2F or RC conversion. Then... just when you think what a turd we got handed, look at what the Apple II got: https://www.youtube.com/watch?v=8WI_QLX1Hhw
  15. So has the relevant binary been found? I kinda doubt it'd use an IOCB/CIO based Format operation since that only works if a valid handler is present, ie provided by a DOS (though that could be explained by reported larger binaries) I'd think more likely it'd use the resident disk handler via $E453 which receives the parms via the DCB and requires no extras.
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