exxos's Atari, Amiga & retro forum

@PhilC You may like to swap those pull-up resistors to 10K ones as that'll reduce the loading on the power rail.

With that changed I can run both CPUs without auxiliary power, just.

@stephen_usher ill give that a try later on, thanks.

I've started work on a Mk.II board using the lessons from the first one.

This is designed to fit around the MMU, which will allow it to sit approximately 3mm lower (flush with the tops of the sockets on the main board).

It also adds control of the /HALT line on the two processors, which should reduce the load on the address and data buses, 0.6mm power traces, the ability to switch between either 2x 256K ROM images or one 512K ROM image and..... an output for a TURBO LED!!!!!

After some Blue Peter style paper cutting I now have the PCB shape sorted and the components laid out.

Now to see if the auto-router (freerouting) can actually get all the traces on!

Well, Freerouting had got through about half the optimisation process, pass 37, with the number of vias down to 81 after 8 hours when I went to bed last night. I'd hoped it would have completed by this morning but instead I found that it had crashed. Of course it doesn't do any checkpointing (*sigh*) so it's back to the beginning again.

By the way, this board is for the C070789-001

P.S. I've taken this as an opportunity to tweak the position of one component to make routing of VCC easier around the CPU sockets and move the auxiliary power connector.

So, this is what the new board will sort of look like.

Kicad obviously doesn't know about sockets and for some unfathomable reason doesn't have a footprint for transistos, so this is showing as a header, and the pin going into the ROM port is sticking up rather than down, but otherwise it gives an idea of what it'll look like.

Let's see what PCBway think of the gerbers. It seems a little cheaper than the previous boards, probably because they're shorter.

Only turned out to be $10 cheaper in the end. Still, the order's placed. I wonder if they boards will arrive before next weekend.

stephen_usher wrote: ↑Sun Oct 18, 2020 9:54 pm Only turned out to be $10 cheaper in the end. Still, the order's placed. I wonder if they boards will arrive before next weekend.

Good luck with the next version.

Thanks!

Would you like any when they arrive or are you happy with the Mk.I?