SUPER STFM MOTHERBOARD PROJECT

Open source STF clone project.
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SUPER STFM MOTHERBOARD PROJECT

Post by exxos » Thu Aug 17, 2017 8:44 pm

Myself and Rodolphe Pineau have long since talked about creating a new motherboard but felt it was a lot of work to which would be very time consuming and costly. Though I have re-visited that idea recently and talked about cloning the STFM motherboard.

Now the first thing people will say, "why not STE", "why not Falcon", "why not Falcon with 060" etc etc. Well, time, cost, and being realistic.

While other "clones" go down the 040,060 route or "emulate" the Atari ST, while a new CPU with all its speed and features is nice, without new software to use all the new features its a bit of a waste. As most software is plain 68000, then a machine should at least run that software without issues. I am not saying I am against new features, I'm all for them, though not at the expense of breaking compatibility with original 68000 software.

My philosophy is , as all the software and games are 68000 based then that should be the CPU to keep. A machine which runs all legacy software just like the real thing. I want the fastest 68000 system possible. True, some things will break with demos and timing dependent code, though like with all my boosters, you can turn off the speed boost to get back to 100% stock state. So people get the best of both worlds.

Firstly creating a new motherboard is not easy, especially when trying to create a whole new architecture. Not only that, parts are hard to find, impossible to solder and we don't want to create something which will become obsolete easily.

My aim for this project is to create a STFM clone only using "through hole" parts. This means people can solder it themselves as there are no SMT parts to worry about. This also makes future modding a whole lot easier.

One problem with the STE is the large SMT IC MMU/GLUE logic. Making changes to the STE circuit is near impossible in some ways. The STFM however, GLUE and MMU are separately so we are able to overclock the MMU for example for higher ST-RAM speeds. So because of this, the STE isn't a good machine to clone. I want to build a machine where parts are relatively easy to obtain and solder.

Of course the STE has the Audio DAC circuit and the jag ports etc. Well those could be added on as a expansion or on future motherboard revisions. My goal here is to develop a open source platform to the STFM world and let people build on what ever they want.

The board in mind is the board I developed most of my upgrades for the C070789. One thing which has become apparent over the years is that the STFM has been updated with all my kits which basically takes over a lot of the motherboard already. Adding up the "cost" of buying all the kits is likely going to be a reasonable sum by itself. Plus all the assembly work etc.

Building boosters has become a nightmare simply due to things like my V2.2 booster needing a 6 layer board in order to keep the PCB size small enough to fit in the original case. If the motherboard had a fast-rom and fast 68000 to start with, then the cost to add a booster wouldn't be much more than adding in the extra PLD logic. Plus no problems with fitting, saves endless hours of routing PCBs in a small area. Multiply that idea with several kits and you get the idea..

We mostly have 6 chip or 2 chips TOS. The first upgrade which normally gets done is to convert to a PLCC ROM which can actually hold TOS102 and TOS104 normally. So the new motherboard would simply have a PLCC ROM. The ROM is easy to change and update and can run at 32MHz.

Similar with the "mars bar" CPU. The DIP maxes out at about 24MHz. Its power hungry, huge and the HC PLCC version is much better. Its lower power, more stable, can run at 32MHz. Having this CPU and ROM as "stock" means adding a 32MHz booster wouldn't be much more than adding in a small GAL / PLD IC.

Similar with 1.44MB floppy drives. Always having to remove the WD1772 just to add a little logic. Similar with adding RAM expansions, never easy. Overall, trying to continue in this direction just isn't realistic anymore.

Not only that, We have PCB layout issues contributing to the DMA issues and god knows what else. It all needs fixing properly. The only way is to just create a new motherboard, one that is more user friendly and basically has various improvements including adding on some expansion ports!

Its the same old story, people want IDE, people want fast-ram, RTC, flash rom, 030 CPU, this and that etc. Well, people will ask why not build all this into the new board ? Well , time and cost. Do people want a board next year or in 5 years time and costing a lot more ? Everyone wants something different. So building a basic machine which the possibility to expand to whatever people want is the best thing to do.

I also want to keep to the original schematics as much as possible. I don't want to build in huge amounts of changes and over complicate it. I want a simple as possible STFM design where people can develop their own addons and use the expansion connectors. The expansion ports will probably follow similar lines to the falcon's expansion connectors. I can speculate that 50% of the STFM area will be free for adding expansion ports. Its possbile 3 or 4 could be added inside for example. There will be larger areas to add future boosters easier like adding a 030 CPU addon card.

Once the STFM has a PLCC ROM and CPU, it frees up a huge area of the PCB already. Similar with the RAM, 2 small DRAM IC's like my MMU kit can give 4MB. So the whole area under the PSU would become free real-estate.

While on the subject of RAM. I did first think of adding on a 4MB 72pin simms. Though its not really future proof. With simms becoming harder to find along with the socket, its not a good idea. The alternative is the 2 DRAM's, but they are SMT. I don't want to do that. I could produce a RAM card , but I don't want to create myself even more work in the future and don't want people to be limited to only buying my RAM card.

After some thought, The idea of using a RAM card like the falcon came to mind. I mean lots of 1MB or 4MB cards are around for almost pennies. It also makes it more future proof as alternative RAM cards can be made if needs be. It also means the MMU and ROM can likely go under the RAM card. This will also save a lot of PCB space and also make the PCB routing a whole lot easier.

The next main obstacle I saw was the shifter area. So many parts. A lot of them are not needed if the RF box is not used. Also a lot of the circuit is generating the 32MHz clock which can be done with a simple oscillator chip. The only thing which is left is the RGB drives. Myself and Rodolphe did look into adding in a video DAC there. Though in the end, we decided its not a good idea. In anycase, the MEGA ST shifter circuit would be used. Its simple, only really needs the Shifter and the RGB drivers. So a lot of parts wouldn't be needed, and saves a fair chunk of PCB space also.

IC's become obsolete, generally get smaller and turn into SMT parts so small they are just impossible to solder by hand. With the simple RGB transistor drives the STFM has, its only a few transistors and resistors. It keeps thing simple and we don't have to worry about parts becoming obsolete anytime soon. I do also think the circuit can be done with less parts like on the MEGA ST. So this in itself keeps parts count down and increases the free space on the motherboard a lot.

A lot of the ST parts are generic. Though things like the MMU, GLUE, SHIFTER, DMA are of course not. Though these are obtainable as spares sold around the Internet, or scrap motherboards etc.

There are a lot of "classic" parts, resistors , caps, TTL chips etc. For the moment they will all be re-created. Though its possible all the TTL chips could be mashed up into 1 single PLD saving parts count and PCB space in the future. Its possible a few parts of the circuit could be tweaked to save parts of PCB space. Though thats wok for another time..

I would have hoped someone by now would have helped create some new FPGA clones for the chips. I would really like a faster MMU using SRAM. ST-RAM is the main bottleneck for speed. Though overclocking the MMU is the only option at the moment. It is also limited to 4MB. I'm sure tweaks could be done to give 14MB ST-RAM like the Falcon. If it was using SRAM then using alt-ram would simply not be needed anymore.

I know there is code for MiST and Suska etc, though I know nothing about FPGA and not really sure those FPGA clones will work on a actual ST machine. Even so, someone would have to develop such things as I just do not have time to do everything myself.

I would think a lot of the "work" the GLUE does is ROM decoding for example. Though in FPGA it would be easy to add in TOS206 support. Though such IC's would need to be 100% cycle compatible to emulate the real ST timings. I don't want to create a ST which breaks anything at all.

Of course any boosters will break a lot of demos which need cycle accurate timings. Though that is the price we pay for speed. My concern here is, if everything went into FPGA, then we basically end up with a MiST anyway. So to a point it would become pointless to create a FPGA based machine as it already exists.

So my aim is to emulate the ST 100%. The only way I see that currently is by using the original ST chipsets. AFAIK, MiST isn't cycle accurate and may have various issue with software. I want to keep the ST design "original". If FPGA can take over a IC 100% cycle accurate then I am all for that.

There are probably a lot of tweaks which can be done. Though we want to get something built now rather than spending the next 5-10 years tweaking everything to death. New boards can be done in the future anyway if needs be. Everything can be in a socket, or even have breakout headers for each IC for future tweaks. So if someone wanted to develop a new GLUE or MMU, then it could simply "plug in" the motherboard. If something went into production, then people using the new Super ST motherboard could simply pop out the old IC and plug in the new FPGA based board.

For starters I want to create the STFM schematic over to Eagle format. Once verified the layout of the PCB needs to be done. It will take some time to make sure all the connectors and such match the original PCB. Once down, that schematic will likely be released but not routed. That would be the "clone" of the STFM board. Basic changes will be done, such as ROM and CPU PLCC packages but not much else to start with.

The whole design would be open source. A lot of "clones" and addons are not and re-creating upgrades over and over is just pointless and a annoying waste of time. As many also are aware, there are so many revisions of the ST motherboard, that its just impossible to create upgrades which physically fit on every revision. So likely around 80% of people around the world cannot even fit my upgrades.

The upgrades which do sell are less than 10 typically in the first year. Spending huge amounts of time on projects which hardly ever sell just isn't a good useage of my time. Don't get me wrong, I'm not in it to make profit out of this, but as I have said many times before, spending months of work on something which only 5-10

As mentioned before, a lot of my upgrades are for the C070789 board. There are several revisions of motherboard and all those people are limited to what upgrades I produce which fit. Its just not realistic time or cost wise to develop the same addon 20 times for fit each revision. Some boards still cannot be upgraded due to SMT MMU etc.

There is also the fact that PSU's are failing where I offer alternatives, but motherboards are failing also. Take for example the video faults I have documented due to caps failing in the video circuit. Every electrolytic is 30 years old now. Servicing such boards is becoming a small nightmare. Again with so many revisions, supplying "servicing kits" for various things is becoming a huge investment, where I do not have unlimited funds, or time or space to go though every issue on every motherboard. A new motherboard would use ceramics as much as possible to prevent similar issues from developing in the future.

The new motherboard will likely cost a lot to prototype. Several prototypes may need to be done. As the cost could be high per board (could even be around £200 a pop). Though by the time the buyer brought all the service kits and upgrades, then the cost probably wouldn't be much different anyway.

My aim is to re-use STFM IC's, possibly also a lot of the connectors and create a STFM "clone" which is basically updated. The STFM clone will be 100% compatible with a real STFM.

Though as mentioned before, adding in boosters or other upgrades can be done easily. Also like my V2 booster, it holds TOS206, TOS104, and can be switched on or off for stock speeds or turbo speeds. The advantage is that it wouldn't any longer need the booster PCB, it would be as simply as plugging in a extra GAL / PLD to enable those features.

The motherboard will likely get designed and made open source. Though my concern is here, again, is the end cost of the motherboard and people being able to assemble them. Overall, if someone purchased a STFM motherboard and fitted all my kits, the cost of the new motherboard probably wouldn't be much different anyway.

I will likely have to set up a kickstarter campaign to fund this in due time. Then it will be up to the Atari community if this "Super ST" becomes a reality or not.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

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Re: SUPER STFM MOTHERBOARD PROJECT

Post by exxos » Thu Aug 17, 2017 8:48 pm

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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.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

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Re: SUPER STFM MOTHERBOARD PROJECT

Post by exxos » Thu Aug 17, 2017 8:50 pm

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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!
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Anzac
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Re: SUPER STFM MOTHERBOARD PROJECT

Post by Anzac » Tue Sep 05, 2017 3:59 pm

Nice work Chris!

following this...
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Atari 2600 Jr - Atari Mega ST - Atari Mega STe - Atari TT - Atari Falcon - SH205 - Megafile 20

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