Sunday, 30 July 2017

NEW STF MOTHERBOARD PROGRESS

So far about 20 hours work into routing. Only 600 wires to go...

I was trying to keep all the PLCC IC's pointing upwards, though it proved not to work out like that.  With address bus on the top of some IC's, sides of others, bottom of others, it just wasn't sensible to have buses wrapping half way around each IC.  So they have been positioned to allow the best flow of routing for the address and data bus.

The MMU to ST-RAM card proved hard going. I had the bank of resistors vertical, though they got in the way of the databus, so moved them downwards and horizontal.  I had to route the MMU area 3 times before I was happy everything was flowing correctly with the layout.

The routing of the ST-RAM card was a small nightmare. As the ST-RAM card is 32bit, it had to be converted to 16bit and then routed to the address bus and then to the bus isolation latches. I managed to do it in 3 layers.  Just no other way to make the routing easier other than developing a new ST-RAM card. Which I may do in the future, but for now its not important.  The 4 bus isolator IC's are located under the the ST-RAM card so it saves a lot of PCB space.

Most of the Shifter has been routed to the bus latches. Also the RGB drivers have been routed. That is basically about it so far.  I think it will take several hundred hours to route in total. So its not going to be done anytime soon!

Some small technicals that so far the address and databus run horizontal across the board.  The bulk of the address bus goes to the PLCC IC's.  Generally only A1-A4 are used on other IC's so they shouldn't be a problem to route from the bottom side address bus to the top of the board.

The databus is across the top of the board as most IC's need access to it, so having the databus accessible near the top, where IO connectors will be is a wise move.

There is something which is becoming apparent, that the IO connectors may not end up in the same order or location as the original board, at least not on this prototype.  It looks like the bulk of the IC's will be located under the PSU. I wanted the shifter to be located next to the RGB connector, but it still may end up some way away. But I will try and squash it down as close as possible. 

Other ports will end up several inches away from where the actual controller IC is. Which isn't ideal. Though as I am trying to keep to the original case layout, then there isn't much choice but to have tracks running across the board. Its a huge waste of space. Though with new cases looking unlikely to happen, then it will just have to be like that.

I estimate a quarter of the motherboard will be used with the new layout I am doing. This leaves 75% "free space" for other expansion connectors.  Probably a large on in the center to allow a 030 addon card. Then some small expansion ports for whatever else.

Now this board is a prototype of the BASIC AS POSSIBLE STF design. I am not adding expansion ports to this , and I am not adding any booster logic (simply because its a long ways of being finished yet and I can only work on one thing at a time!)  This board will be as small as possible to keep prototyping costs down and will just be used to verify the ST actually boots and everything works as it should.  I guess this could be called a "Mini STF"

Once this is done and tested, then I will work on a re-design to match the STF's case layout. Once that work is done then whatever space is left will be allocated to expansion connectors.  I will then have to design a new booster series to fit this motherboard and do testing etc. So we are probably looking at 12 months+ worth of work here. Though I hope the initial prototype will be manufactured sometime over the next 6 months.

This also means I do not have any time to develop new addons. So those who want USB, HDMI, LAN, GFX CARD and everything else, well you yourself will have to develop that and create a addon card as I just do not have anymore time to work on anymore projects.  My hands are full trying to keep stocks up in my store and I am a long way off finishing my booster work. So I am probably going to be maxed out work wise for several years yet.

I have had a LOT of suggestions for tweaks and mods. A lot are just not possible as they are just to time consuming.  Though smaller mods like DRIVE AB Jumper swap and speeding up the serial port can be done easily and will likely get done next revision. 


A lot of issues are down to limitations of the MMU. For example, 14MB ST-RAM isn't possible with a new MMU.  It will also likely need new GLUE logic as well. So its not so simple. I just don't have time to develop a new MMU. If someone wants to develop a MMU clone which will allow 14MB ST-RAM and allow SRAM to be used, at 32mhz clock speeds, then pleased develop a solution I can plug in and try out.  If it works then it could be included as standard in future revision.

Though so far I have asking for help with this for almost 10 years now. I know of the MiST code, I know of Suska code.. its means nothing to me. I have no idea about FPGA, or VHDL and I just don't have time to mess about with it all.  I have my hands full with so many projects that I just don't have time to develop a new MMU on my own! So while it would be awesome, and open the door for many mods, I just have never seen anyone willing to step up and take on the project.

I also get a lot of "why don't you do this" or "why don't you do that".. Well, I am doing it all my way and doing what I want to do, end of discussion.  If people want something more than I am developing, then go and design and develop the bloody thing instead of dumping 50 projects on my door stop for me to design all on my own. I'm not saying I am closed to suggestions, but people have to be realistic on what this new motherboard will entail and the amount of work involved.  I will provide the ground work for people to develop what they want. If people don't develop anything for it, then don't complain to me about it!

As for my upgrades like the CPU boosters. I am just going crazy routing the CPU socket to a PLCC CPU every time.   I mean wiring up data bus to data bus, address bus to address bus, like 50 times over is just not fun anymore.  I have several designs of boosters which never saw the light of day. Plus several revisions of each version.  It boils down to basically replacing the 68000 CPU each and every time on each and every booster board. 

It would just make a lot more sense to have a motherboard which simply has a fast 68000 built on so I just don't have to spend endless hours basically routing the same thing over and over.  Addon logic would just be a few wires in a small PLD.  Upgrades can be done many times faster and save me endless hours of work! I also am tired of fighting "noise" issues on the motherboard. It probably takes up 90% of the development time for each project as I have to debug and trace random issues.

I personally want to create a solid universal platform to be easily upgraded.   As said before, its just madness to keep spending time trying to develop upgrades for a machine which just isn't upgrade friendly.  I would rather spend the time designing this new motherboard and fixing all these issues to allow faster addons to be developed in the future. 

Some people just dont get why I am re-creating the motherboard and not making huge changes. Well thats not the aim of this project and isn't the point in this project either!

So that is my basic overview for the "goal" of this project and some information as to why I am doing this. If the community want to make this into a more powerful ST then people will be able to easily build on my designs and improve and make any changes they want.


4 comments:

  1. Whatever you do, just make sure to have fun! :)

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  2. Looks like one of those weird star charts to me and just as complex :)

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  3. Keep going Chris! If you need a hand for the routing, let me know!

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