[Coco] Pop Star Pilot - Chapter 11 is up

[John Kowalski]

Nick Marentes wrote:
>Thanks John. I'll give it a try.
>I'm still concerned with compatibilty with emulators.
>The prompt in the loader is easy and guaranteed to work though.

Oh, there will be one more difference between using the fast and slow
timer clock sources.
The slow one is triggered *on* the hsync, and the fast one is just on
'x' clock counts, so it won't trigger at exactly the same horizontal
position as the slow timer interrupt.
slow = on the 3rd hsync after you enable it.
fast = trigger 342 (3 scan lines worth of) CPU cycles after you enable it.

So using the fast timer will shift the interrupt horizontally
depending on what horizontal position (within a scan line) the CPU was
at when it enabled the timer.

Anyhoo.. it just means you might have to adjust your code timing a wee
little bit since it'll trigger interrupts at a slightly different
position.  The trigger points might be half a scan line later when
using the fast timer than when using the slow timer (they still happen
at 3 line intervals, just the trigger point is offset)

I can't say how emulator compatibility will be..  they keep improving
them so maybe it's ok.  Way back, none of them had the timer exactly
right.  I believe MESS is now specifically modeled to emulate the '86
version.  I mentioned once to Tim Linder that most CoCo 3 software was
programmed on an '86 GIME and It was only after the '87 version came
out that people started noticing some effects not working properly
(like the color chart in CoCoMax III or stutter or flickering in some
games...) so emulating the '86 version would run more programs
correctly than emulating the '87 version.

-- 
John Kowalski / Sock Master
http://users.aei.ca/twilight/sock