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Re: TF536 + 68000 relocator and ROM board project.

Posted: Tue Nov 10, 2020 9:50 pm
by exxos
stephen_usher wrote:
Tue Nov 10, 2020 9:45 pm
Well, it helps a small amount as the circumferance of the wires I'm using is still far greater than the width of a track and the routing is far more direct too. The resistance certainly is far lower.
DC resistance lower yes, AC resistance no. Larger dia wire gives higher eddy currents which basically increases the inductance.. Increased dia only helps when your using hollow copper tubing or something. You could solder on 1cm thick copper bus bars and it wouldn't help. You can really go down the rabbit hole with it all.. just easier to stick to ground planes and just not have to think about it full stop :)

Re: TF536 + 68000 relocator and ROM board project.

Posted: Fri Nov 13, 2020 11:39 am
by stephen_usher
It looks like PCBWay have built the 4 layer boards and they should be out for dispatch later today, probably arriving in the middle of next week.

Re: TF536 + 68000 relocator and ROM board project.

Posted: Wed Nov 18, 2020 8:48 pm
by stephen_usher
The 4 layer boards should arrive tomorrow, so I've been scavenging parts from the old boards.

Let's hope the new boards solve all the problems (and, indeed, work!).

Re: TF536 + 68000 relocator and ROM board project.

Posted: Thu Nov 19, 2020 11:16 am
by stephen_usher
OK. A spanner in the works. DHL usually phone to ask for duty payment as it's in transit. This time they didn't and just held delivery.

It's taken me about half an hour trying to find how to pay them, searching the DHL web site fruitlessly. I had to Google in the end and found the right place on the second page of searches. They don't make it easy.

Re: TF536 + 68000 relocator and ROM board project.

Posted: Thu Nov 19, 2020 11:44 am
by exxos
I know what you mean. Think it was fedex who can't pay online, have to ring them up.. takes over a hour to do a 30 second task :roll:

Re: TF536 + 68000 relocator and ROM board project.

Posted: Fri Nov 20, 2020 10:35 am
by stephen_usher
Out for delivery! *bites nails* Will the PCB work?

Re: TF536 + 68000 relocator and ROM board project.

Posted: Fri Nov 20, 2020 3:29 pm
by stephen_usher
The new boards have just arrived and they buzz out OK.

I should have time after work to build one up. Then the proof will be in the pudding.

Re: TF536 + 68000 relocator and ROM board project.

Posted: Fri Nov 20, 2020 5:22 pm
by stephen_usher
Bother! Doesn't work for some reason. It looks to be something to do with the ROM decode area.

If I have PIN 1 of the GAL connected then A17 is dead weird.

Oops! I forgot to solder the Vcc pin on the GAL!

Re: TF536 + 68000 relocator and ROM board project.

Posted: Fri Nov 20, 2020 5:33 pm
by stephen_usher
That was it! D-oh!

Power and ground are almost flat now, so that's good.

As usual I've a bit of dodgy surface mount soldering.

Re: TF536 + 68000 relocator and ROM board project.

Posted: Fri Nov 20, 2020 5:58 pm
by stephen_usher
OK, it's fixed the low performing 68000, so it was obviously the Power/GND noise which was causing the CPU to miss clock cycles.
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