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CIA 6526 chip used in Commodore 64 is capable of controlling two separate joystick buttons. But the second button should be connected through paddle pot input. This option was not popular till the release of Commodore 64GS (Game System). C64GS came with Cheetah Annihilator joysticks that officially has two separate buttons.

Apparently, several two button game have been released after C64GS. But I couldn't find the names. So what are the two button C64 Games?

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  • I don't think your statement about the hardware is true. It looks to me like C64 controller ports (each) only support 5 digital inputs. So, 4 joystick directions + FIRE. Do you have a reference for how 2 buttons could be supported on a 4-direction joystick given this controller port limitation?
    – Brian H
    Mar 16 '17 at 15:59
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    Hi @BiranH, second button is connect to the Pin 9. It is an analog input pin used for paddle PotX. You can check the wikipedia page or Lemon64 Forum Topic about it.
    – wizofwor
    Mar 16 '17 at 18:56
  • Prior to USB, the standard PC interface for joysticks was through the midi port, and used 2 analog lines for axes apart from 2 digital lines for 2 buttons. Digital D-pads would just connect 0, 50 & 100 KOhm resistors to the axes lines to represent left, center and right, so the same could be done for the 2 analog lines, the C64 is theoretically capable of reading a full byte out of each, so it provides 8 bits, thus 8 independent digital buttons. I can imagine this may not be that reliable, but getting 2 or 4 buttons out of it should work fine.
    – Petruza
    Jul 15 at 13:57
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I haven't personally tried myself but searching on the web suggests that below games make use of the second joystick button wired to Pin 9 POTX signal. If played on a C64, functionality is already assigned to relevant keyboard controls.

Myth - History in the making

Robocop 2

Last Ninja Remix

Here are the relevant discussions.

http://www.lemon64.com/forum/viewtopic.php?t=35034

http://www.lemon64.com/forum/viewtopic.php?p=358186

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