Amiga Demo Scene CD Idea

[alexh]

done some more work on this today. To save people time the following demos do not quit nice. Its a shame but they cant be included

Grind.
eld-dust
eld-riseandshine.

That is surprising because if you look at the last frame of the following video... it exits to AmigaOS. I wonder if there was a "final" release?

[alexh]

Code: Select all

https://files.scene.org/get/parties/2020/gerp20/amiga_demo/fd_1992.zip,fd_1992,runme.bat

[terriblefire]

Ah that is a shame, those are good demos for showing off 060 power.

An idea. You mentioned using the NVRAM. Is it possible to save a flag for CPU speed? So the initial boot you would set a speed that just this demo CD reads. Some people might not be able to pass 50Mhz, but others could have fans etc and sit at a higher MHz no problem. And a lot of 060 demos love extra MHz.

(Thinking about it, I suppose we will be burning the image once done, so I guess we would be free to set 'Setspeed Speed=' in the startup -sequence. The NVRAM option would be cleaner and allow easier sharing of the finished .ISO)

Yeah TBH this is a software thing. The NVRAM tools i've found are confusing tbh. I just want a command line tool to save and restore some environment variables.

[terriblefire]

That is surprising because if you look at the last frame of the following video... it exits to AmigaOS. I wonder if there was a "final" release?

i'm testing on FS-UAE and it gets into a state at the end

[terriblefire]

Code: Select all

https://files.scene.org/get/parties/2020/gerp20/amiga_demo/fd_1992.zip,fd_1992,runme.bat

I like this one but the end credits loop forever. So cannot use it.

They must exit without interaction.

[terriblefire]

Code: Select all

https://files.scene.org/get/parties/2020/gerp20/amiga_demo/fd_1992.zip,fd_1992,runme.bat

I like this one but the end credits loop forever. So cannot use it.

They must exit without interaction.

Ok i have found a way to make them exit after X seconds if the floppy drive is still clicking during the demo.

[terriblefire]

I've made a good deal of progress on this and have built an ISO and sent it to a few to test.

Huge help from @erique. We found some demos that would not run from CD but were fine from read only hard disk. With much checking/debugging we found that the CDFS.LIBRARY in the CD32 does not handle SEEK from the end of a file due to a sign bug. This means that any executable with HUNK_OVERLAY (which demos tend to do to save ram?) will fail to load.

The code in cdfs.library deals with SEEK_END as .. .

Code: Select all

        /* OFFSET_CURRENT  = 0 - Add the current position */
        /* OFFSET_END      = 1 - Offset from end */
        /* OFFSET_BEGINNING=-1 - Already a byte position */

        if (mode == 0) pos += fc->ReadPtr;
        else if (mode >  0) pos = size - pos;

Which is wrong... When you pass a offset from the end of the file you pass a -ve number. So we had to patch 2 locations from a sub to an add..

I then got the cd to loadmodule DOWNGRADE cdfs.library and bingo. The demos now run.

[alexh]

Cool.

I don't own a TF360 but when I eventually do, I know I'll want something like this.

[terriblefire]

So a couple of people have been testing the demo cd and observed that the CD drive speed is frankly pitiful. I still want to produce this for lulz but it might push me into thinking about improving the cd speed on the cd32.

[alexh]

Would it improve CD performance by simply adding buffers in AmigaOS? Will the CD32 AmigaOS CDFS then read-ahead?