Open source STF clone project.
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Post by exxos » Fri Aug 18, 2017 7:37 pm

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It seems a lot of people are not "following" the basic changes I am wanting to make with the STFM.

Basically the ST-RAM area is being removed in favour for the Falcon 4MB ST-RAM cards. Or even 1MB ones. There should be a lot of those floating around since a lot of people are replacing their cards with 16MB simm adapter cards (like the ones I make).

I did wonder about using 2 small DRAM IC's like I do on my MMU upgrade, but I don't want to move to SMT parts currently. It may become a option in the future, but there are other factors to think about.

Mostly with the Falcon RAM card sitting higher up, its not actually taking up motherboard space. So like on the Falcon where the ROM is located under the ST-RAM card, I can do the same. In fact the MMU can be located there. Possible even the GLUE and CPU.

It is then possible that the RAM card could go under the floppy drive. With the MMU, GLUE, CPU also under the ST-RAM card and CPU. Basically half the motherboard is now free from parts. This generates the room for the expansion ports like on the Falcon.

Another good thing is the CPU is close to important things, like RAM, ROM, DMA. So it would solve all the noise problems relating to DMA write failures etc.

The RF port, Well, I asked peoples opinions on Facebook and its clear people don't use it anymore. I haven't for 20 years easily. The thing is, a LOT of parts around the shifter and the RF circuit itself, its creating a lot of parts and taking up a lot of space. While it may be "nice" to have it, I think sacrificing a expansion port for it isn't a good deal. Not only that, its more parts which increases the cost of the thing. So likely the RF port will go. This would make the design actually a "STF". The MEGA ST does not have a RF port either and lots of people use those just fine.

I am also being asked a lot of questions about this project. I can't say much about it as it is nothing more than a "idea" at the moment. Work is ongoing on the motherboard design and will continue until I have something which can be physically built and tested.

Once this motherboard is tested and I am happy with it. Then I will think about expansion ports and layout. As mentioned before, likely all the CPU lines will be routed to each connector. Just about every upgrade needs access to the address and data bus.

I may also add 2 large expansion connectors (like expansion connectors on the falcon) for things like a 030 booster, or video card etc. I may also add in some smaller expansion ports for maybe things like Hard drives or LAN for example.

Before people get excited, I am not developing video cards or LAN cards. Similar people would prefer HDMI video output, well, I would as well. But there is no solution of this either. Others will have to develop such addons if they want those options. I just do not have time sorry!

All I can say for video, is I have tweaked the RGB drivers to give better outputs. Though I have no plans to do anything more with the video circuit. What I may do is drive the video from the 12V rail and add in some simple 78L05 regulators on each RGB driver to stop "cross talk" between RGB channels. I do see some odd interference in the video due to noise. In part bad regulation in the shifter circuit, but also long tracks picking up noise in the motherboard itself. So I want to reduce that as much as possible.

That so far is the "plan". This is going to keep me busy for some time.
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