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by stephen_usher
Sun Oct 25, 2020 11:39 am
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

I know. That was intentional as the last board which did have it was picking up a huge amount of noise from it, and it made it impossible to cut the ground connections for experimentation. Also, where most of the traces go there's no room for the fill. It would only really be able to be done under t...
by stephen_usher
Sun Oct 25, 2020 8:40 am
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

It's definitely a ground noise problem. I cut the ground traces to the CPUs and wired up a direct wire from the pins going into the main board to the "68000" socket. The noise was a lot less and no more memory errors. There's a long trace which goes around the top of the "68000" socket which seems t...
by stephen_usher
Sat Oct 24, 2020 8:22 pm
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

Putting the two leads of the scope at either ends of the data lines to compare the traces doesn't show much difference. At the far end the high values are ver-very slightly attenuated and that's it. The main difference, again, is the amount of noise on the power and ground. I'm guessing that the gro...
by stephen_usher
Sat Oct 24, 2020 6:02 pm
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

I've soldering in the second 68000 and am running tests on that now. It's a lot better now, but there is some memory corruption still. The floppy works. It's definitely something taking the machine beyond it's operational range. Next will be pull-ups, when I can remember where I put the bag of matri...
by stephen_usher
Sat Oct 24, 2020 5:22 pm
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

More specifically it's when it reads from the floppy.

I may try putting some pull-ups on the data bus as that looks the most scrappy.

Having said that I'm now getting memory errors again, and bits being set on the screen which look a bit like address offset errors.
by stephen_usher
Sat Oct 24, 2020 4:42 pm
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

I have been looking and I can't see anything obvious. Maybe the address/data lines are a tiny bit more noisy but that's about it. It's probably tipped something just over the edge when accessing the DMA chip, which is what the floppy hangs off. It also doesn't see the UltraSATAN on the ACSI bus (it ...
by stephen_usher
Sat Oct 24, 2020 4:17 pm
Forum: CHAT FORUM
Topic: If you're in the UK, get your retro stuff before the new year!
Replies: 31
Views: 413

Re: If you're in the UK, get your retro stuff before the new year!

What about the 5000 euro registration fee in each EU country?
by stephen_usher
Sat Oct 24, 2020 4:13 pm
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

Oh yay. It's started bombing as soon as there's a floppy access now, even in the diag ROM.

Swapped back to the Mk.I just to make sure that the base machine's OK and everything's fine. Phew!
by stephen_usher
Sat Oct 24, 2020 3:37 pm
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

Those memory errors were due to a bad CPU. Swapped the m68k and the fault went away.

Still, it doesn't seem as stable as the Mk.I board so far.
by stephen_usher
Sat Oct 24, 2020 2:42 pm
Forum: TF536 ST EDITION
Topic: TF536 + 68000 relocator and ROM board project.
Replies: 180
Views: 4023

Re: TF536 + 68000 relocator and ROM board project.

It boots to diag cart now off the "Accellerator" socket but it's picking up memory errors. Also the /HALT & Turbo LED GAL is getting *VERY* hot. I'm guessing that my LED circuit design is faulty and it's drawing too much current from the GAL pin. And somehow I've managed to change the ROM switch sen...

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