exxos's Atari, Amiga & retro forum

Of course I talk about doing away with the TTL chips in favour for tiny logic, generally using more SMT stuff... Also I found there is a PLCC 68901 (MFP) So that could be used to save space.. Video circuit is of course on track to using less bits... I already condensed the RS232 circuit and other parts...

Though if anyone else has any ideas then post here... I mean things which are possible, not putting everything in one FPGA, because that is suska ;)

One other minor step might be to replace the 6850s with equivalent logic in an FPGA - IIRC there is a register-level replacement for a 6850 as part of one of the existing 8 bit retro-computer designs - and even a small FPGA should still have lots of resource left to mop up lots of other simple bits of logic.

I'm not sure of the etiquette for linking to an external site but I can PM the link if it would help?

You can link here...

FPGA main problem is 3.3V or lower IO voltages...

If they would fit in a 5V PLD then it could be possible...

I need to try the FPGA core to see if its small enough to fit in a PLD actually..

Again this question also depends on what your ultimate goal is. Anything can be made smaller but what do you sacrifice in doing so? Is 100% compatibility and ports being all in the right place a necessity? As I mention a lot, you can always fit one board on top of another similar to the Ram board and that's instantly reduced the motherboard footprint.

I think you could save a lot of room if you either cabled the ports to headers on the boards or moved them, even placing some above the others.

Just a tbought again but it's juggling compatibility with future goals.

Good luck :D

What about the SEC you are using in your booster. Replacing the PLCC 68k with that directly on the board should gain some space?

If the main ASICs could be converted to FPGA models, then the possibility of running nearly the entire system (apart from the IO ports) at 3.3v is there.

Icky wrote: 01 Nov 2018 00:24 What about the SEC you are using in your booster. Replacing the PLCC 68k with that directly on the board should gain some space?

The SEC isn't the same as the 68000.. it has some missing pins which have to be emulated by a PLD...

https://www.exxosforum.co.uk/forum/viewt ... =110#p5938

exxos wrote: 01 Nov 2018 10:21

Icky wrote: 01 Nov 2018 00:24 What about the SEC you are using in your booster. Replacing the PLCC 68k with that directly on the board should gain some space?

The SEC isn't the same as the 68000.. it has some missing pins which have to be emulated by a PLD...

https://www.exxosforum.co.uk/forum/viewt ... =110#p5938

Right so not a direct replacement.

With SEC and PLD this would not reduce size very much or even at all I guess. Interesting project though (SEC Booster) and following intently.

Icky wrote: 01 Nov 2018 10:54 With SEC and PLD this would not reduce size very much or even at all I guess. Interesting project though (SEC Booster) and following intently.

My plan is to add the DIP 68000 socket on the next remake board, this way the SEC booster can be used on the STFM and remake boards.

Ultimately the PLCC 68000 which is currently on the remake board, will likely be removed once the SEC design is proven to have no issues with anything... Possibly be integrated, but I think having the CPU on a expansion card makes it easy to remove and upgrade in the future. Plus of course, I only have two design one booster for two different machines.

exxos wrote: 01 Nov 2018 11:01 Plus of course, I only have two design one booster for two different machines.

Thats the most important keeping your costs, development, etc in one place makes it so much easier for you.