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Demos Amiga Demoscene Archive Forum / Coding / Dump OS or Not (n00b question)

 

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nonarkitten
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#1 - Posted: 28 Aug 2018 02:27
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I see most (all?) demos seem to dump the OS right away without hesitation. When targeting machines with 68060's, it doesn't seem like the OS would really take much CPU time away from the demo, so is there another reason for dumping the OS besides a tiny bit of extra horsepower?
dodke
Member
#2 - Posted: 30 Aug 2018 14:31
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I guess it depends on what you know already (and laziness). If you don't kill the OS you'd need to code everything in a system friendly way. If you're used to banging the hardware directly then it's easier to just kill the OS and do your usual stuff.

Some demos are system friendly with support for RTG and/or AHI.
rloaderro
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#3 - Posted: 31 Aug 2018 06:04
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I used to have a quite system friendly setup with RTG/Cybergraphics support, double buffering and all handled by the system calls. Amiga-M would work and everything. In there everything was done using chunky to planar though and this essentially mean you become locked to less than or equal to 25 fps for all effects. I wanted to mess around with bitplanes, copper and sprites and have a chance at > 25 fps effects so I needed something new.

I had a go at creating a completely system friendly demo which still uses some hardware such as copper/sprites when doing Neonsky. I figured that with 060 the system overhead would not cause any serious problems.

I found the system is hogging sprite 0 for the mouse pointer at all times. You can still use it, but whenever the user moves the mouse, sprite 0 will also move no matter what you were using it for.

Building dynamic copper lists using the system API was really sluggish too so I ended up with poking some pointers in some system struct somewhere to make it use my own copper list behind the scenes. It didn't feel like it was the correct way to do things.

I felt I spent more time on trying to figure out system's display inner workings instead of coding effects so I dropped the system for any display tasks. Still I'm keeping it up so it can be used for harddrive loading etc.
nonarkitten
Member
#4 - Posted: 4 Sep 2018 23:24
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dodke:
I guess it depends on what you know already (and laziness)

Haha. Well, based on hacking around, going through the OS is often a lot more work than hitting the registers.

rloaderro:
I wanted to mess around with bitplanes, copper and sprites and have a chance at > 25 fps effects so I needed something new.

Did you ever exceed this?

rloaderro:
I felt I spent more time on trying to figure out system's display inner workings instead of coding effects so I dropped the system for any display tasks. Still I'm keeping it up so it can be used for harddrive loading etc

So for fast C2P and other display hacks (and especially if you want all sprites) then that part of the OS has to go. But it's convenient for IO (which makes sense).

Thanks a lot for the insights.

 

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