SUPER STFM MOTHERBOARD PROJECT

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.