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terriblefire

Posted Wed Oct 26, 2016 2:37 am

Just to let anyone who is interested know that i've started a project to create Amiga accelerators starting with the most basic one i could think of ... an A500 68020 accelerator.. A video of the first prototype running is on my channel "terriblefire"

https://youtu.be/QqDn7l8Fia0

Everything is up on github but the UCF file is currently for the patched rev1.

https://github.com/terriblefire/tf520

I am about to do an assembly video for the rev2. I havent managed to get 16Mhz running stable yet.

https://github.com/terriblefire/tf520

After i have verified it works you can order the bare PCB at :-

http://dirtypcbs.com/view.php?share=...300398d2ff0048

(of course you can just grab the Gerbers and order them from the board house of your choice... but this link is particularly cheap and i get $1 per *order* (i.e. 10cents per board) which helps me keep developing prototypes). I'm not doing this for profit. I just think a lot of people want to make hardware for the Amiga and we should start standing on each others shoulders to make progress.

I'm also designing the 030 + FPU version and that will be going to the board house in time for Xmas.

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intric8
Seattle, WA, USA
Website

Posted Wed Oct 26, 2016 10:00 am

@terriblefire this is amazing work! I love how you're rolling up your sleeves and just going for it. Very impressive.

Are you planning on focusing mainly on the 500, or do you think other models (1200, 2000) might find some love, too?

You rock! And definitely keep us in the loop as you continue to make progress. I'd be happy to do a promo/review at some stage. Super cool!

FWIW, I have a souped up 1200 running one of Jenn' accelerators, and I love it. I also just acquired a mint, never used 2000 (NTSC) that really should be in a museum somewhere, hence my selfish and self-interested question about about other models. ;)

I also have a 500, but only have so much desk space.

Where are you based, if you don't mind my asking?

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terriblefire

Posted Wed Oct 26, 2016 12:59 pm

intric8 wrote:@terriblefire this is amazing work! I love how you're rolling up your sleeves and just going for it. Very impressive.

Are you planning on focusing mainly on the 500, or do you think other models (1200, 2000) might find some love, too?

You rock! And definitely keep us in the loop as you continue to make progress. I'd be happy to do a promo/review at some stage. Super cool!

FWIW, I have a souped up 1200 running one of Jenn' accelerators, and I love it. I also just acquired a mint, never used 2000 (NTSC) that really should be in a museum somewhere, hence my selfish and self-interested question about about other models. ;)

I also have a 500, but only have so much desk space.

Where are you based, if you don't mind my asking?
Hi,

The accelerator should work in the 2000 and 1000 without much fuss (and also the Atari ST - but it may need some firmware patches).

I'd love to do 1200 and A4000 boards but i want to walk before i run. Maybe a cd32 accelerator?

I'm based in Glasgow. I'll be posting progress on twitter and youtube... all @terriblefire.

I will keep everything open so that if I disappear due to work etc then others can pick up where i stopped.

Cheers
Stephen

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terriblefire

Posted Thu Oct 27, 2016 2:23 pm

Hi all,

I managed to confirm this evening that the Rev 2 board fixes all the glitches from the Rev 1. I still have some bugs in the CPLD firmware to iron out. I also made up one of my new 68020 breakout boards. The breakouts will let me put a logic analyser on the board and follow the CPU at start up.

https://twitter.com/terriblefire/status ... 9569988609

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intric8
Seattle, WA, USA
Website

Posted Thu Oct 27, 2016 9:38 pm

Very exciting!

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terriblefire

Posted Sun Oct 30, 2016 11:37 am

I found an issue with my board today.. or more precisely I found that the 7Mhz signal at the amiga is so poor it causes modern logic chips to glitch. I'll need to look for a solution.

User avatar
terriblefire

Posted Sun Oct 30, 2016 11:49 am

Hi all,

I made a bit a bit of a discovery today that hopefully will help anyone else building an accelerator for the A500 or B2000. In a nutshell the 7Mhz clock that appear at the CPU is dreadful and glitches like hell on anything modern. I spent a bit of time looking at this with my 100Mhz analog scope before hauling my whole setup over to a friends who has a 500Mhz scope + logic analyser.

We were able to see that the drive strength of the 7Mhz clock from Angus is pretty poor under load. We tried the following simple verilog code on various Xilinx and Altera CPLDs...

always @(posedge CLK7M) begin

OUT <= ~OUT;

end

(we also tried it as a counter and explicitly setting values).

Basically the 7Mhz clock is jittery enough to make this happen at the output..

https://twitter.com/terriblefire/status ... 1720535040

We tried adding various resistor/capacitor loads on the clock to smooth it out but it either didnt help or cause the amiga to stop working.

I am going to try putting a non-inverting schmitt buffer on the 7Mhz clock and see if that helps. Unfortunately it means i'll need to respin the design. If the schmitt doesnt solve it then i'm stuck pulling C1 and C3 from the board which is an ugly solution.

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intric8
Seattle, WA, USA
Website

Posted Mon Oct 31, 2016 10:55 am

Your Twitter link breaks, but I can imagine it's not good.

Sounds like you've definitely found yourself in a difficult spot. Thanks for keeping us in the loop! Good luck with your next solution.

UPDATE:
Your Twitter link is working now. Although I must admit I've no idea what I'm looking at. Makes me a bit envious...

User avatar
terriblefire

Posted Mon Oct 31, 2016 2:03 pm

It looks all fancy but really its just Jenga...

https://twitter.com/terriblefire/status ... 7469056000

Hopefully the buffer will cleanup my clock so that the middle signal on my previous tweet will follow the top one.

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terriblefire

Posted Wed Nov 02, 2016 1:53 pm

So with a bit of clock fixing i managed to get this working.

https://twitter.com/terriblefire/status ... 7736389632





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