rfox@sdcsvax.UUCP (Richard Fox) (11/04/84)
Here's a stomper for ya. How is the clock and the user port 1 related? It looks as if user port one can somehow ground out the clock or slow it down. For the 100,000 dollar question --> WHY? If any one has noticed that when the joystick is plugged in the user port 1 and is pulled all the way to the left the clock cycles seem to be slowed down by a factor of almost 10? If any one has noticed this idiosync. of the C64 please post why. I will try and solve the little problem - rich UCSD
miller@uiucdcsb.UUCP (11/05/84)
Most of these questions have been discussed before by us "old timers". I realize, however, that new people are always joining the group. What you described with port 1/west/fire button not pressed is that the c64 uses the same hardware to read its keyboard. Hence, some joystick configurations get mapped into chars. That particular situation maps to the Control key, which, as everyone knows, slows the screen scrolling down if the cursor is at the end of the screen. A. Ray Miller Univ Illinois
cuda@ihuxf.UUCP (Mike Nelson) (11/06/84)
It slows things down because the joystick ports are polled by the same hardware as the keyboard is. Some of the joystick positions map to keys. The effect of pulling the joystick in port one all the way to the left is the same as holding down the CTRL key during a listing. As far as I remember they are electricly identical. Happy Hunting Mike Nelson AT&T Bell Labs ihuxf!cuda
doug@terak.UUCP (Doug Pardee) (11/12/84)
> If any one has noticed that when the joystick is plugged in the user port 1 > and is pulled all the way to the left the clock cycles seem to be slowed > down by a factor of almost 10? If any one has noticed this idiosync. of > the C64 please post why. I will try and solve the little problem - > > rich > UCSD Shooting from the hip... No, I never noticed, but I'll speculate about the cause anyway. Moving the joystick to the left is the same as pressing the CTRL key on the keyboard. The keyboard is scanned at 1/60 second intervals by using the 6526 timer interrupt. The clock is kept by counting 60 such interrupts as one second, etc. A feature of the 64 is that holding the CTRL key down will slow down screen scrolling enough that you can read it. Now, for the Olympic event, conclusion broad-jumping. The slow-scroll feature is probably provided by a delay loop in the timer interrupt routine whenever the CTRL key is held down. This makes for a significant delay before requesting the next interrupt, 1/60 second later, so that the 6526 timer interrupts are much less regular than 1/60 second. Good luck chasing it down! Doug Pardee -- Terak Corp. -- ...!hao!noao!terak!doug