Monday, 7 August 2017


100% routed :)

Well maybe not exactly as I have a epic amount of tidying up to do yet.  I also need to add in de-coupling caps and the reset switch has gone AWOL.

The "back" IO connectors are basically in the right place. Though I need to measure a real motherboard and make them align with the case properly.  The Cartridge and midi ports are just plonked on just for testing.  As this board is a lot smaller than the original, Then alignment doesn't matter at this point.

I will probably add in a single IO expansion port onto this. Then at least at some point I can route the alt-ram stuff into a card.  Once working, I *might* add that into the next design as a stock feature. Or it may be a custom IO card which may fit under the PSU.   Currently there isn't any room for anything under the PSU, not a expansion card anyway. Though I think a right angle connector which is dedicated to alt-ram would easily fit there.  Then at least its not taking up a main expansion port then.

It has become apparent that the TTL chips, inverters etc, are actually getting in the way of "good" routing.  There isn't much I can do about that. Though I am half wondering about replacing them all with a couple of generic 22V20 GAL's.  Then at least I can make the layout of the chip better to suit my PCB layout.  As it stands, the TTL chips are actually making the design a bit of a mess :(

Similar with the ST-RAM card. Because the Falcon card is 32bit, this means a lot of double routing to convert to 16bit.   There isn't much that I can do about that. Though the bus isolation buffers are also a huge mess of tracks. Again, I may just replace them with a larger PLD. Though I am not sure at this point if its a good idea to move away from dedicated TTL chips or not.  For example, I don't want to force people in the future to use Altera chips (which is what I am using currently).

Ultimately, there will be some more "glue" logic. Which will contain the booster logic. That will be Altera most likely. Though at least it is a optional extra.

So the plan now is to finish off the current design. Lots of messing about with stuff to do now. But it is 100% routed now!

I had a program running to check time to route it, and its about 28 hours! 36,000 left button mouse clicks and mouse moved about 3.5miles!  Considering the work involved I think 28 hours is a huge accomplishment. Of course it will take a lot more time to add in the booster logic, IO expansion headers and other stuff. Though at least this is something now which is almost ready to be prototyped!


  1. Great work Chris... when do you think you will be in a position to boot your 'ST Remake' board for the first time...?

  2. Its actually bootable as it is now (aside from I need to add some caps). I just decided to make some small changes for including a test addon card, which I didn't plan on doing this revision. But as there is some room, I decided I would.

    As to getting some prototypes made, hard to say. Though I think over the next few weeks I will start thinking about a physical board to build up and test.

  3. I had a good laugh when I saw the "Bad DMA" in your design ;) Pretty impressive I have to say...

  4. Piling on the miles :p
    Bad DMA lol

  5. Yeah, all DMA's are bad so..... :)

  6. This looking better everyday Chris! I know someone can help with the gal to hdl conversion (in case you don't make it already). S. Leary he can make it with his eyes closed :p

  7. I've put in my order to him for a new MMU some time ago ;) Problem is, he tends to get distracted to easily ;)

    1. hehe yeah Stephen is a good friend, always ready to help.