exxos's Atari, Amiga & retro forum

rubber_jonnie wrote: 12 Apr 2025 23:00 AFAIK the board doesn't have to be populated with RAM for the other parts of it to work.

That's really good news.

:)

HigashiJun wrote: 13 Apr 2025 03:15

rubber_jonnie wrote: 12 Apr 2025 23:00 AFAIK the board doesn't have to be populated with RAM for the other parts of it to work.

That's really good news.

:)

When I built the OSI 600 I had to source the RAM from Ali Express. I got lucky and all 20 IC's were good. It's the same RAM but 48 chips, so hoping I get as lucky again...

I may buy in batches.

Tested physical assembly today:


And it's looking good. Just need to fit the Molex power plug to the mainboard to feed the 610 board.

I can't power on yet though as I have missing IC's, but will hopefully have those soon :)

OK, so the 610 is completed bar the RAM:


And it looks great. Only one problem though, this:


Now here's the thing, this happens when this cable that joins the two is just plugged into the 600 and not even connected to the 610 board on top!!!


So I buzzed out the cable and there are no shorts on pins next to each other and all the pins buzz straight through. Once again, just plugging the cable in makes the computer stop working, it's very weird, it's not the 610 expansion board, it's the cable.

:dizzy:

I guess that's transferring the address, data and r/w lines on the bus? Cross talk or capacitative loading on the bus?

stephen_usher wrote: 23 Apr 2025 16:27 I guess that's transferring the address, data and r/w lines on the bus? Cross talk or capacitative loading on the bus?

It is.

That's what I thought too, or it was acting as an antenna, but expected when it was plugged into the 610 it wouldn't be an issue, but it still fails. It's about the same length as cables I've seen on other builds.

When the socket is empty, which it normally is, the 600 boots fine. Plug in the cable and nope.

Have you 'scoped the bus to see if it's ringing? The signal could be reflecting off the far end of the cable.

stephen_usher wrote: 23 Apr 2025 17:12 Have you 'scoped the bus to see if it's ringing? The signal could be reflecting off the far end of the cable.

I haven't, but I found the problem:

It seems that despite the guides on the connector, the cable shifted during assembly and rather than cutting into individual wires, it joined some together.

I've re done the dodgy end and voila, it boots.

:yay: :girldance: :dualthumbup: :yay2:

:cheer: :girldance: :cheer: