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Author Topic: Natami and FPGAArcade  (Read 11222 times)

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Offline FrenchShark

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Re: Natami and FPGAArcade
« Reply #14 on: May 01, 2009, 02:29:41 AM »
Hello Mike,

let me finish the testing of the SID first.
I have seen the die scans but no detailled documentation except for the analog filter.
I am thinking about implementing a pseudo stereo mode too.

I also have the VIC-1541 being implemented in VHDL but it still has some bugs (IEC lock-ups). My guess is that the 6522 or 6526 implementations are not perfect.

Regards,

Frederic
 

Offline FrenchShark

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Re: Natami and FPGAArcade
« Reply #15 on: May 05, 2009, 04:30:47 AM »
Hello Mike,

I have one question : what is the part number for your slide switch ?
I am using one that is rated for 500mA 6V (which is enough for my design) but the one on your board seems a lot better.

BTW, I am still working on the SID. It looks like I need to have part of the digital audio processing with signed numbers...

Regards,

Frederic
 

Offline mikej

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Re: Natami and FPGAArcade
« Reply #16 on: May 05, 2009, 09:42:45 AM »
Yeah, it took me a while to find a suitable small switch.
It is eswitch ra tl1105-rf100q digikey EG1837-ND fits.

I prefer to use offset maths for DSP work, it is easier to see in the simulator.
Say your input is 8 bit 0 to 255.

This could mean the signal is -128 to 127 if the value 128 is taken as 0.

If you want to use signed numbers you can still use std_logic_vector (in VHDL) - just remember that the number is signed so invert and add one where appropriate.

It's just wires, so it's how you treat the value which matters.
/Mike
 

Offline alexh

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Re: Natami and FPGAArcade
« Reply #17 on: May 05, 2009, 12:53:57 PM »
Bare in mind the FPGAArcade board has no hardware 68060 CPU. Meaning anything you create on this board will be as slow as hell.

Plus isnt Natami just "vapourware"?

We've seen no real evidence that they are doing anything, other than talk bollocks most of the time.

Non of the "technical" discussions they have ever go beyond the "high level idea" stage. There are no posts of technical investigations, nor implementation level ideas.
 

Offline alexh

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Re: Natami and FPGAArcade
« Reply #18 on: May 05, 2009, 01:10:04 PM »
Quote

FrenchShark wrote:
Quote

mikej wrote:
The only license issues are with the C64 SID at the moment but this will be resolved.

Yep, what's wrong with the SID ?

Was the SID in v0.27 of FPGA-64 non functional?
 

Offline AJCopland

Re: Natami and FPGAArcade
« Reply #19 on: May 05, 2009, 02:48:06 PM »
Quote

alexh wrote:
Plus isnt Natami just "vapourware"?

We've seen no real evidence that they are doing anything, other than talk bollocks most of the time.

Non of the "technical" discussions they have ever go beyond the "high level idea" stage. There are no posts of technical investigations, nor implementation level ideas.

Thomas demo'd the orignal C-one developed Natami FPGA work with a 68030 quite a while ago now so the basics of the AGA and some of his extended modes have already been shown. The new revisions are the "vapour" part of it in that it's not done yet.

The rest of your critique feels a bit harsh though. Most of what gets discussed in the public part of the forum is really high-level because no-one wants to get bogged down discussing every little detail in there. That was part of the reason for Thomas not wanting to involve others in the project originally.

Plus everyone's a volunteer so the updates that get done are just done in 5 minutes by whoever has a spare moment. Some weeks no development gets done at all because everyone's got a life, family and jobs.

Lately there's been a flurry of activity with people writing test cases for the cpu simulation so that it can eventually get to compatibility with something like a 68EC040. But thats not planned for another year or so probably. The current 060 based natami is still being built by Thomas with the 060 on a daughter board "060 card" and that's what'll be released first for people to get to use, just a few boards to begin with.

The much over discussed 3DCore will either be at a basic level by then (maybe just missing a lot of features and modes) or it'll just be released later. The softCPU planned, calling it 680x0 whatever may come even later than that, although its the part seeing the most development right now.

I'm not saying that everything is perfect and going to be out immediately or that there isn't a lot of rubbish talked about it but it is happening. It's just pretty damned difficult to do so it's taking a long time. :-)

Andy
Be Positive towards the Amiga community!
 

Offline mikej

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Re: Natami and FPGAArcade
« Reply #20 on: May 05, 2009, 03:32:04 PM »
I haven't checked Peter's latest release. In the last version of the code I ported the SID wasn't present due to some license issues. I asked Peter if things would change and he is working on it. In the meantime I can't redistribute that code, and I don't believe in releasing binaries.

/Mike
 

Offline freqmax

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Re: Natami and FPGAArcade
« Reply #21 on: May 05, 2009, 03:39:20 PM »
AJCopland, Where are these "test cases for the cpu simulation" ..?

Test programs to verify 68020 compatibility would be great. They can be built with existing computers without access to FPGA hardware or skills.

Softcore MMU-68841 and FPU-68881 would be great for unix.
 

Offline AJCopland

Re: Natami and FPGAArcade
« Reply #22 on: May 05, 2009, 03:44:42 PM »
They're checked into the SVN repo' and you can see the titles of the posts in the "Team" tab of the NatAmi forums. There's a lot of bug reports about them at the moment but there's been a lot of those resolved too :-D

The guys doing that stuff are testing them on Amiga's as well I believe, I don't do anything with that side of things at the moment.

Andy

PS: there's no plans for an MMU or FPU at the moment. They're just aiming for EC-type compatibility such as 68EC040.
Be Positive towards the Amiga community!
 

Offline alexh

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Re: Natami and FPGAArcade
« Reply #23 on: May 05, 2009, 04:19:29 PM »
Quote

mikej wrote:
I haven't checked Peter's latest release. In the last version of the code I ported the SID wasn't present due to some license issues.

The last release was C-One binary only :-(

I thought that if you go back a few versions the SID HDL was present albeit without filters?

http://pacedev.net/
 

Offline FrenchShark

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Re: Natami and FPGAArcade
« Reply #24 on: May 06, 2009, 05:11:07 AM »
Quote

mikej wrote:
Yeah, it took me a while to find a suitable small switch.
It is eswitch ra tl1105-rf100q digikey EG1837-ND fits.

Thanks! I will update my PCB with it:-).

Quote

I prefer to use offset maths for DSP work, it is easier to see in the simulator.
Say your input is 8 bit 0 to 255.

This could mean the signal is -128 to 127 if the value 128 is taken as 0.

If you want to use signed numbers you can still use std_logic_vector (in VHDL) - just remember that the number is signed so invert and add one where appropriate.


In the SID, I generate the waveform with unsigned then, before multiplying it with the envelope, I flip the MSB.
Then, I mix the 3 voices (and the DC offset) together and multiply the result with the volume. Finally, I flip back the MSB to have unsigned for the 1-bit DAC.
The 1-bit DAC has a 64x oversampling (linear interpolation) and a first order sigma-delta. I will try a second order later.

Quote

It's just wires, so it's how you treat the value which matters.
/Mike
 

Offline freqmax

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Re: Natami and FPGAArcade
« Reply #25 on: May 06, 2009, 02:24:34 PM »
As for SID cloning. This seems to be the most serious:

http://en.wikipedia.org/wiki/MOS_Technology_SID#Hardware_reimplementations

"The PhoenixSID 65X81 project (2006) aimed to faithfully create the SID sound using modern hardware. The workings of a SID chip were recreated on an FPGA, based on interviews with the SID's creator, original datasheets, and comparisons with real SID chips. It was distinguished from similar attempts by its use of real analog circuitry instead of emulation for the legendary SID filter. However, the project was discontinued, because George Pantazopoulos, who was the head of this project, died on April 23, 2007, at the age of 29."
 

Offline mikej

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Re: Natami and FPGAArcade
« Reply #26 on: May 06, 2009, 03:43:14 PM »

I had a number of email conversations with George before he died. He was very proud of his SID, and we had an agreement I could release the code when it was finished. Sadly this never happened.

This is why I never released Peter's C64 code (which was missing a SID at the time) on my website, and why I have started to look at it again for the new board.

/Mike

 

Offline freqmax

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Re: Natami and FPGAArcade
« Reply #27 on: May 06, 2009, 05:13:23 PM »
Now that he's dead it maybe it can be useful to release any code such that others may continue where he didn't finish?

Btw, why did he die?, he was way to young to die from natural causes.
 

Offline FrenchShark

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Re: Natami and FPGAArcade
« Reply #28 on: May 07, 2009, 01:52:40 AM »
Quote

mikej wrote:

I had a number of email conversations with George before he died. He was very proud of his SID, and we had an agreement I could release the code when it was finished. Sadly this never happened.

This is why I never released Peter's C64 code (which was missing a SID at the time) on my website, and why I have started to look at it again for the new board.

/Mike



I have seen his website too.

Concerning the filter, the digital version of the state variable filter should be close enough.
There is a good explanation here:
http://www.earlevel.com/Digital%20Audio/StateVar.html
We certainly need some non-linearities in the feedback loop. I am thinking about using a look-up table made with a block RAM and some interpolation.

BTW, mike the part number you posted was not the slide switch next to the power connector. It is a momentary switch (for a reset button maybe ?).

Regards,

Frederic
 

Offline mikej

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Re: Natami and FPGAArcade
« Reply #29 from previous page: May 07, 2009, 09:40:46 AM »
I've no idea what happened to George, he just stopped writing me emails one day :(

I'm an idiot, I have the part numbers the wrong way round in the BOM. That would confuse the production people.

The correct part number is
mountain switch 102-1261-ev. Digikey EG1837-ND fits the footprint.

Best,
Mike.