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Black Belt Jones
Account closed
Registered: Apr 2002
Posts: 57 |
HD friendly demos?
Allllrighty then,
HD friendly demos, is that a viable possibility? Going from:
http://www.neef-online.de/tac/lxdemo.htm
which seemed to have stopped being updated a long time ago, is there anyone else doing this? Is it something that would eventually catch on, or is it too much hassle and stuffing around with timing and code to make this a common thing?
Are there enough HD users to make this popular? i'm asking cos i use a CMD hd and even though theres just a handful that will run on a native partition its a pretty cool idea.
just a thought... anyways, back to la la land :-) |
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cadaver
Registered: Feb 2002
Posts: 1160 |
Well, if a demo uses a 1-bit IRQ loader, you only have to modify the drivecode a bit (*), timing etc. doesn't change at all. This way demos can be made compatible with 1581, CMD-FD and CMD-HD. 2-bit isn't much harder, just needs taking care of the drive CPU speed aswell, which is 2MHz with those (afaik)
But adding IDE64 support needs ditching the IRQ loader completely and becomes much more pain, as the IDE64 read routine might disable interrupts for some time.
(*) = if demo is using custom 1541 sector read routine you'll most probably have to modify it to use jobcodes, which may constitute more than "a bit"
I'd hope for more programs made compatible "out of the box" in the future atleast, only need to detect the drive + upload appropriate drivecode in the beginning, while C64 side of the loader stays the same. |
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Derision
Registered: Feb 2002
Posts: 69 |
I thoug that the CMD HD had a 1541- 1581-native mode built into it somehow? |
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Black Belt Jones
Account closed
Registered: Apr 2002
Posts: 57 |
yeh it does have 1541 emu, but most demos are timing intensive and bugger all works... |
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cadaver
Registered: Feb 2002
Posts: 1160 |
I guess in the emu-mode hardware registers still stay same (CMD-HD native), so you can't just write to $1800 in the drivecode and expect it to work. |
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Stryyker
Registered: Dec 2001
Posts: 468 |
CMD emulated the disk layout via their emulation partitions. On top of this they emulated job code and track and sector areas in memory. That was about it. Most ZP are different. A number of ROM jump in routines are different. They never fully emulated the entire RAM or ROM or IO, which is sort of a pain but partly sweet. I know when I got into coding for the FD 2000 it wasn't too hard as the AR could load from it thinking it was 1581. From there it was easy tweaks to the old 1 bit IRQ loader I was using (from Weird Worlds by Excess). The hardest to write for would be the CMD HD series as no emulator handles them. VICE you can use 1581 emulation to get most stuff sorted for the FD series. |
