| Posted By
TMR
on 2014-11-08
05:27:22
 |  Converting SID tunes to the Plus/4
i've just got a couple of questions about converting SID tunes to work on SID card equipped machines.
Obviously the SID registers themselves need to be remapped but where's the best place to use for compatibility and, if there are a couple, is there any way to "auto detect" a SID card or do i need a menu before the program starts?
Also, are the note frequencies different? And if they are, is there a resource online with the right values for a PAL machine?
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Posted By
gerliczer
on 2014-11-08
07:02:21
| Re: Converting SID tunes to the Plus/4
The best bet for register remapping is address $FD40. It is supported by all available cards, AFAIK. Some cards also support $FE80. It is of course auto-detectable, as normally these addresses have no connected device behind them, therefore reading these addresses return either the last data bus content or then undefined state of the floating bus. Having SIDs mapped to these addresses results in the expected behaviour, namely reading write only registers will always return the usual value ($FF I think).
The old cards are running at 90% of the C=64's speed, so they sound quite differently. BSZ's new cards have the capability to run the SID at the same speed as in the C=64, but that's not the default setting. It is also capable to use the original $D400 address to program the chip. I suggest to read the documentation at http://bsz.amigaspirit.hu/nae/index.html. Probably it will give answer to most of your questions.
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Posted By
Luca
on 2014-11-08
07:09:22
 | Re: Converting SID tunes to the Plus/4
$D400 -> $FD40
We used to keep up with the Csory's SIDcard and its $FE80 SID addressing just because traditionally the most spread SIDcard (The Solder's one) has been built up to be compatible to the earlier Csory's one, and the new from NST follows the trend. If you look at our Hardware page, we still don't know how the heck is done that $FE80-driven stuff  Marq splittedThe First Ball Plus/4 in two different versions, one for $FD40 and one for $FE80 and I still don't know why (I told him he only would have needed the first one but he followed another way...).
Autodetecting SIDcard should be easy, as booting a Plus/4 with SIDcard on entails to have all zeroes in the $FD40-$FD5F/$FE80-$FE9F areas with the value $FF into $FD59 $FD5A $FE99 $FE9A, memory areas usually filled with their respective hibytes once booted up the machine (#$FD/#$FE). Uselessly deeper, NST's SIDcard has its own flag to achieve this, and there's a little example in the manual (get it online) about how to detect if the card is a Solder's one or not.
And about the frequencies question: yes. I myself used in the past to compose a tune for one machine and then apply some changes in the slide/glide stuff in order to fix it for the other one. Of course there is also a global shifting in the notes while playing a tune on its non-native iron...but I'll leave all this to TLC, which is the real expert here 
What I can suggest is to read all the text TLC did write for SIDwinder V01.23, I've copied and put straight on its page just for this kind of needings. Most of all, read the Specific Plus/4 Notes!
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Posted By
TMR
on 2014-11-08
07:24:49
| Re: Converting SID tunes to the Plus/4
Thanks both, i've passed on some notes to Sean (Odie) and the SIDWinder link. Is YAPE the best bet for testing this stuff under emulation?
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Posted By
Luca
on 2014-11-08
07:34:09
| Re: Converting SID tunes to the Plus/4
Absolutely yes. Nice to hear that Sean is again on a 264 machine after Reaxion!
EDIT: I answered to the question containing "for this kind of stuff". If some more tech is involved, SID stuff apart, plus4emu shows the closest-to-real-iron emulation.
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Posted By
Chronos
on 2014-11-09
15:15:00
 | Re: Converting SID tunes to the Plus/4
i always mapped it to fe80 but after i read this topic, i'll keep it in my mind.. 
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Posted By
Luca
on 2014-11-09
16:36:42
| Re: Converting SID tunes to the Plus/4
Chronos: ah, so you are the living demonstration it works with both addressing!
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