Re: SID talk

Johey wrote:

Welcome androSID! I bought eight perfectly working 8580 chips from you a few years ago, for the MB6582 box. Happy you found your way to the Replay side. big_smile

Hello Johey! I'm glad you're happy with the SIDs and it's nice to meet you again.

Re: SID talk

Androsid, you don't happen to have some 8580's for sale? smile

78

Re: SID talk

MikeJ wrote:

androSID and I have been having a good chat on email, which has already led to a few layout related improvements to the code ...

Sounds good  big_smile

/WoS

79 (edited by ColinD 2015-02-11 21:41:43)

Re: SID talk

Hi Guys, Just signed up.....

I've delved into the Sid in the past and have written a couple of players/editors, and a friend also has done much the same as we were feeding off each other so to speak.....  didn't have any tech/scene contacts and no tips etc at the time...

From what I've gathered..... Five things to note so far....  (Thanks to this internet thing !!)

As far as I know, Jeri's implementation didn't implement the filters....

There is a DC offset somewhere in the design.... When you change the Sid Main Output volume level, the DC level also changes with the attenuation....  This is why you hear a 'click' when you change volume levels.   This is used and abused to play crude sampled sound...   on the newer revision sid chips, the dc offset was lower or gone, so samples using the 'old player' code don't quite work so well....

There are some other funky sid tricks to get better D>A conversion for samples using one of the voices and I think the test bit ? - Not sure exactly how it works, but its probably something like starting a high ish frequency triangle or saw tooth, and then stopping it at the desired level and will be an exact cycle timing thing based around a sweet spot frequency matched to the code.  The value of the triangle ramp when stopped must stay at that level....  Kind of a reversed take on an old skool AtoD technique based on using a comparator and a ramped voltage - and the time taken to ramp up is equivalent to the analog input value - Doing this in reverse is probably as simple as starting the wave form off, and then jumping into a list of nops with the reset code at the end, the earlier you jump into the code gives more nops and a higher output, but don't quote me !!  ( you would maybe have 32 nops and the frequency ramps up over say 40 us or something - 25 khz or something, or whatever the highest frequency is ?)

There is a sid bug when a voice is first gated....  There are a couple of different software workarounds to solve this and its well documented.....(Called Something like a 'Hard Reset/Restart' to get stable predictable and repeatable results/sounds )   One of my friends made a nice music editor back in the day and it sounded great on a real c64 (I'd have to check this, so don't quote me), but with the modern emulators you get the odd click here and there...  When we were developing sid editors and players back in the day, we didn't have any tech contacts/networks from the scene and were working fully isolated from knowing any tricks/fixes as above...  certainly didn't know about this Reset/Restart Trick....  Our Players seemed to sound fine on both of our machines - Maybe my friends player is a bit whacky ?? !!

The Sid has been emulated with an Atmel Mega or something, but side by side comparison shows some issues and looks to me to be lagginess when funky stuff is going on and its deffo struggling to keep up with some of the clever player tricks and stuff.....  https://www.youtube.com/watch?v=uXQMQXl_Uyw  and also  https://www.youtube.com/watch?v=M6I4xr0sTlw  - However this is in Software Emulation and not True Hardware emulation.....  I would imagine that some demo's would push it easily beyond its limits, like examples below....

Hope this provides useful. 

This will probably freak you all out....and gets interesting at 4:30 or so  https://www.youtube.com/watch?v=oY-78oQ8hrw

And this too.....  https://www.youtube.com/watch?v=MDrqBYkco-Y

Another Demo... Playing AMIGA Mods on the C64 using the Sid with 8 bit samples.. No Joke - Gets good at 2:00 or so and lots of info in the scroll text !! - https://www.youtube.com/watch?v=ZMioAPZcays

Cheers, Col

Re: SID talk

Colin,
Welcome, nice to have you here. Thanks for the info.

The development has been parked for a month or two while we catch up with other stuff, I'm picking it up again now.
The current design is based on IC layout extract and analysis. It's close to bit perfect, but there are a couple of known issues still to fix and verify. The analogue part if modelled with a digital filter, but it's pretty arbitrary at the moment.

The next step is to mount a real SID on my board and run the FPGA in parallel - and monitor the osc/env registers every cycle on both devices. We'll also compare the audio outputs on a digital scope.
I'm upto my eyeballs working on the public file repository, testing boards and getting this new generic framework in place!
Cheers,
Mike

Re: SID talk

Hi, Mike!

Did you have a chance to work on this project recently? It would be great to get working SID FPGA model.

Re: SID talk

Hi. Not yet, although I did have a play and agree it sounds horrible sometimes.

83

Re: SID talk

Mike, I wouldn't fully blame the SID in all cases, there is still the chance that it might be caused by some CIA issue or so (means: some hick-ups in timing).

But this is quite hard to track down. I had some plans to connect a real CIA on the expansion board as you do, but it takes quite some time to set up and debug and I will start only if I know I have enough time to pull it through in one step. So it is not my highest prio for now  - the games I like to play work fine and sound is good enough big_smile

/WoS

Re: SID talk

Don't know if you lot has seen these?

https://www.youtube.com/watch?v=VBxKlTipDII
https://www.youtube.com/watch?v=EU-xA0BW9Ms

Re: SID talk

interesting!

Re: SID talk

and...I've finally found the DIL ZIF socket I bought years ago for my SID measurements.
All set to play now.

Re: SID talk

Board built !

Need to add the analog bits around the SID tomorrow and hook it up.
This will allow me to start comparing the operation with the soft core.

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Re: SID talk

Excellent! So looking forward to this :-)

Re: SID talk

It just occurred to me I can test both the VIC and CIAs in here as well. I know Wolfgang has done this already to some extent, but might be handy. I'm going to try running some of the latest demos.

90 (edited by gpz 2017-02-14 22:23:10)

Re: SID talk

Mike, I wouldn't fully blame the SID in all cases, there is still the chance that it might be caused by some CIA issue or so (means: some hick-ups in timing).

this is actually unlikely - unless a tune is using samples, the timing doesnt really matter much - even a few rasterlines of jitter (several hundred cycles) between calls to the player are not noticeable in most cases.

Re: SID talk

We'll check em all.

Re: SID talk

Thanks to Daniel, some chips for me to test - and my SIDs off to be checked too.
Cheers,
Mike

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Re: SID talk

I'm more than sure that the SIDs you've received are relabled!

They are working possibly... but I'm sure they are not make CW21/1982