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About FizzyChicken

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    Space Invader
  • Birthday 05/03/1971

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    Merseyside, Little England.

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  1. Thank you so much for the feedback. I'll forward your reply to the author of that ROM.
  2. Thanks. I am testing against both Javatari and Stella. One of my test ROMs has graphical glitches on Stella which are not present on Javatari (https://javatari.org/?ROM=http://www.mousefingers.com/atari2600/2020.bin), so I wasn't sure which one was most accurate. I will continue testing on both though and investigate getting some hardware.
  3. Thanks for the info. I only mentioned Javatari as that is the one on the 8bitworkshop site. I am also checking my work against Stella. I do not currently own any 2600 hardware, but if I were to buy one how what would be the best way to run my own code ? Some sort of eprom cartridge ? Thanks.
  4. Hi. I'm writing my own 2600 emulator and I'm using the tutorials on 8BitWorkshop.com as test cases so I can see if my emulation is matching Javatari. I have an issue with the tutorial in chapter 8, color sprites. In this code the horizontal position of P0 is never set, yet in the emulator it appears half way across the screen. In my emulator, since the horizontal P0 position is never set, P0 is currently off-screen. So my question is... what is the default horizontal position of the hardware sprites if you don't actually set them ? Is this documented anywhere ? Thanks.
  5. Hi. I'm writing a 2600 emulator and I'm looking for rgb values for the palettes the machine used. I know I should probably work them out with luminance and value etc. but I just want some quick rgb values to throw in for now so that I can see if my TIA emulation is working sensibly. Thanks.
  6. I'm writing my own 6502 emulator and was wondering which instructions are affected by Binary Coded Decimal. Is it just ADC & SBC, or do INC, INX, INY, DEC, DEX and DEY obey BCD rules when the flag is set ? Thanks.
  7. FizzyChicken


  8. Just spent a couple of hours retyping your code in and making sure I understand what's actually happening. That kernel was all a bit strange until it 'clicked' in my head. Thank you for doing these posts... it's blowing my mind how clever 2600 coders need to be .
  9. Wow. Some good tips there. I learnt to program the 6502 on the C64/128 when I was a kid. Used to do demo's and rip games apart etc. The only other asm I've done is a couple of years coding 68K on the MegaDrive. The 2600 is quite a challenge after 20-odd years of making games with higher level languages and tools. Absolutely loving getting back down to the metal again. Makes me feel like a big kid .
  10. Hi, as I understand it when the 2600 is powered on the PC is set by the reset vector, which is held in ROM memory locations $fffc & $fffd. But when a 2K ROM is inserted the ROM only reaches up to $f7ff. When I look at the hex dump of Combat I can see the reset vector ($f000) in locations $f7fc & $f7fd. So does the reset vector location depend on the ROM size or am I missing something ? Thanks
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