exxos blog - random goings on

[exxos]

So this is what the next-gen Falcon ST-RAM board would basically look like.

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[Badwolf]

Typique!

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[Badwolf]

So this is what the next-gen Falcon ST-RAM board would basically look like.

Inline termination resistors?

Not going to use 4-way packs?

BW

[exxos]

Inline termination resistors?

It's a "T" type filter. 2 resistors in series with a center tap to a cap to 0v. It's the only way to squash it all. It does help decouple noise going back and forth between the videl and RAM as well.

There is still a small amount of noise on the RAM side but it's below 200mV and not ideal probing .. Well, don't care :lol: I've beefed up the power rails a bit to see if that helps as well.

Been trying to figure out the impedance of it all. I think 1mhz into 100pf was about 1.5k. So the videl shouldn't see to much abuse from the filtering. :shrug: The rise time goes from about 6ns to 12ns. But unavoidable really. Overall even if there is more of a load on the signals, it can't be as bad as having all the abuse from all the oscillations and spikes anyway.

Edit:

RC filter basically. Filters out crap over about 30mhz.

[Badwolf]

Inline termination resistors?

Its a "T" type filter...

Aha, proper EE stuff. :stars:

I know you're not hand assembling them, but that many passives makes me itch. :P

BW

[exxos]

Aha, proper EE stuff. :stars:

I know you're not hand assembling them, but that many passives makes me itch. :P

You can have a PCB if you want :P

Getting them assembled other than the RAM. I'll have to try and transpose RAM from a already built board to keep it a fair test. Not looking forward to going through all that again.

[Badwolf]

You can have a PCB if you want :P

Ah, that's very kind but it turns out I have a surfeit of RAM boards now! :lol:

BTW, I've been working on resuscitating my last DFB1r5 board today (the one I earmarked for you, but melted a socket on).

Progress! Two bodge wires so far...

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Just a problem with DMA, I think. Hopefully just one more bodge.

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[Badwolf]

Yep, BGK was broken. Another DFB1 enters the world.

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Only a 36MHz oscillator in there, so 224% is about right.

Now, three bodge wires in the top half of the chip is disappointing. I'd better check the lower half of the data bus before I even think about soldering on any SDRAM. Also: not sure I have any, actually :P

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[Badwolf]

TT-RAM all good (40MHz oscillator this time):

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The only issue is that the FPU doesn't work. I seem to remember I had a problem with this socket when I first fitted it. It may just need replacing, but this board is so beaten up and the FPU is such a fickle beast anyway, I'm not going to attempt it myself.

So, @exxos, this one's for you to play with. I'll chuck it in the post on Monday. :)

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[exxos]

The only issue is that the FPU doesn't work. I seem to remember I had a problem with this socket when I first fitted it. It may just need replacing, but this board is so beaten up and the FPU is such a fickle beast anyway, I'm not going to attempt it myself.

So, @exxos, this one's for you to play with. I'll chuck it in the post on Monday. :)

OH nice one :yay: :yay:

I will probably break it before getting to the FPU tests anyway, so all good :twisted: :twisted: If something lasts more than 10mins in my hands, then you can considering it a more final design :lol: :hide: