Re: SID talk

I have had the die shots for a long time, and performed some layout analysis. I am talking about getting  a microprobe on the device to make some measurements while it is running.
/MikeJ

Re: SID talk

I'd love to join you there, Mike. Such open heart surgery is ever thrilling tongue
Please keep us posted.

Re: SID talk

The trick is to get the die exposed in such a way the chip still works.... Hopefully the lab can do this.
/MikeJ

p.s. I would really appreciate donations of any flavour of SID chip to practice on. Apparently it's often the filters which suffer ESD damage, so the best candidates would be working chips which have poor sound quality.
Once we have the hang of it, we'll do a good one ...

Re: SID talk

I'll see what I can find. Some friends of me stacked up 20-30 C64-s a few years before.

Re: SID talk

oh cr@p, I have to get going on my SID then pronto. Wolfgang is fast..
I've just ordered 10 6581s from my local shenzhen supplier. I don't expect them to work - or even be original, but they did promise to test them. Good for decap practice anyhow.
/Mike

Re: SID talk

@Mike: I've scored a cheap C64-II as a donor so if you don't mind getting a 8580 then I could post it with the Miggy as well.

Re: SID talk

Mike, don't you have an Amiga core to finish first? wink

Re: SID talk

Yes, but the C64 has been in the works for a very long time as well.  Mike is just picky about how the hardware level re-creation (a step beyond emulation) turns out.  This is why he wants to see the SID for himself and not use existing pieces that do work, but perhaps not exactly as they should.

Re: SID talk

Artlace wrote:

@Mike: I've scored a cheap C64-II as a donor so if you don't mind getting a 8580 then I could post it with the Miggy as well.

YES YES YES, Wolfgang wants to make friends with a real VIC chip as well!!

35

Re: SID talk

MikeJ wrote:

oh cr@p, I have to get going on my SID then pronto.
<...>
YES YES YES, Wolfgang wants to make friends with a real VIC chip as well!!

Take your time - still a long way to go, this was just the easy task - I am just getting faster in setting up new directories wink

Yes, have some high interest in NTSC-type VIC and VIC-II as reference, so if your source has some of them in exchange of some hard currency would be great...

/WoS

Re: SID talk

@Mike: Off it goes with the SID then! I'll do my best to send the whole parcel this week(end).

Re: SID talk

@Mike: a 8580 & 8565 is here pushed into styrofoam, waiting to be shipped. Hopefully I'll get around it tomorrow.

Re: SID talk

Fantastic,thanks - but make sure it's anti-static foam! Styrofoam can build up a lot of static charge which can damage the chips. Wrap the sytrofoam with some aluminium foil first if you can.
Cheers,
Mike

Re: SID talk

Uh, hopefully I didn't kill them. I'll wrap/package it accordingly.

Re: SID talk

@Mike: SID+VIC has been shipped, hopefully it will get to you fingers crossed.

Re: SID talk

I know it's a bit of stretch but would it be possible to put your core in a small FPGA on a PCB and use it as a SID replacement? All the alternatives we have so far are mediocre.

Re: SID talk

We could even interface that SID in FPGA to something like the Raspberry Pi... and have a Linux based SID synthesizer tongue

Re: SID talk

Or keep it in the Replay but interfacing it with the Amiga core, and then make an AmigaOS based Paula+(multiple)SID tracker... Oh those wet dreams. smile

Re: SID talk

johey, THAT would be something!!

Re: SID talk

Artlace wrote:

I know it's a bit of stretch but would it be possible to put your core in a small FPGA on a PCB and use it as a SID replacement?

I wonder if it would fit into an FDIL V2 wink

Re: SID talk

Yeah, sure it would - not sure how much filter DSP we can fit in there.

Re: SID talk

Once I get a known good SID of each flavour, and before I poor acid on and stick needles in them... I was thinking of trying something less invasive ...

How about this :
If we run a real SID in parallel with the digital portion of the FPGA clone, and stick the output of each into a 'scope, it should be possible to compare the volume settings,waveform shape etc of each correct? We can verify the timing of the test bit, and even the LFSR sequence is correct?

I've also got a reasonable spectrum analyser here.

If I was to set up a square wave at freq X, and then run through all filter params and record the output on the analyser, does anybody have the knowledge to convert this back into state variable filter params?
/Mike

48

Re: SID talk

Better would be even a network analyser for non-destructive tests:
AFAIK the SID als has an external input connected to the input of the filters. So basically doing a black-box analysis to find the different poles and zeros of the network should do the job (network analysers can provide also s-parameters etc.). When using several SIDs of the same version but different production dates, they could be correlated to improve the results further. I don't expect the analogue filter network is that complicated, when looking at the time it was designed (and how much time was used to design it). I need to check, maybe I can get my hands on such an analyser (if it can be used for such low frequencies is then the second question - our equipment is usually in the GHz range sad ).

About the LFSR: For the Namco starfield generator I used a brute-force approach to check all possible 16bit polynomials by folding the generated series with the measured series from the pixel dots. This run took just a few hours over night on a ordinary PC - and I was able to find the matching polynomial (and I also proved this way that it was the only polynomial with a 100% match). Here it is even simpler, it is only required to check the assumed 23bit polynomial (x^22+x^17+1) against the output pattern (but only if I find this program again I set up that day...).

/WoS

Re: SID talk

Oh, I forgot about the external input. Quite right. I might have a network analyser here at work.

I checked in my WIP m6581 into the top of the c64 source directory - we may want to move it later.
It's based on the code we found out there, which in turn is based on the interview with the designer. I'm re-writing and checking against known layout findings as I go.
/MikeJ

50

Re: SID talk

MikeJ wrote:

I checked in my WIP m6581 into the top of the c64 source directory - we may want to move it later.

Tried to update to hook it in - where can I find it? Is it on SVN?

/WoS