STE V1.5 32MHz BOOSTER - STATUS

[PaulJ]

This is the first one which will be heading to my store.. 36MHz WS ON. I will leave it on for a couple of hours then onto the next one for testing...

Out of curiosity what does the bottom of the board look like.. the plug in part you designed? If you have the time.

[exxos]

Out of curiosity what does the bottom of the board look like.. the plug in part you designed? If you have the time.

Very unexciting...

bottom.jpg (68.49 KiB) Viewed 3394 times

[PaulJ]

Wow.. same connection as some of the memory upgrades. You have my admiration attempting to make a accelorator that plugs into a PLCC socket that way!! Getting the pin alignment perfect and keeping it that way has got to be a challenge. Personally I'll stick with accelorators that plug into dip sockets or are soldered in. As you have ranted in the past we all know the reliability of PLCC sockets and the issues they cause. You have a set of stone that would make a award winning prize bull jealous! You are the master!!

[exxos]

Yes, plug in stuff isn't great, but as people were breaking their STE trying to remove the old socket.. its the lesser of the 2 evils..

Yeah, pin alignment took 3 or 4 or 5 PCB attempts to get it right Probably mentioned it "somewhere" in the tread..

[exxos]

https://www.exxosforum.co.uk/atari/store2/#0147

2 in stock currently.. will be more later (when the 3D printing has finished) . I'm classing them as a BETA board due to recent chaos Worst case is I will have to start knocking them out with a 32MHz OSC.. but will see how the 36MHz ones hold out in the wild first.

EDIT:

While this booster runs at constant 36MHz for higher than 8/36Mhz switching for example.. Its actually making the CPU warm up a lot more which doesn't really help overclocking. If I get chance at some point, I will put the CPU into 8MHz when accessing the bus to see what the overall slow down will be...

[exxos]

I have been trying for the past few hours slow down the CPU on bus access (more time in 8 MHz mode like the previous V1 booster).. While this works, it actually works out slower running at 36MHz than the V1 running 32MHz. This is because the asynchronous clock needs to be synchronised which adds delays into the logic. I have tried all sorts to avoid this but it just isn't going to work

For example the benchmark below.. is 36MHz but with 8/36 switching...

836.jpg (55.82 KiB) Viewed 3423 times

Versus the V1 32MHz booster...

ste32mhz.jpg (52.21 KiB) Viewed 3423 times

It is pretty close in both cases, but even so, its still not totally stable.

<rant>

These problems really just come down to trying to speed up the on-board ROM access. This access is all done in the 8MHz domain, so syncing it to the faster clock domain, adds delays. Without the delays, it does actually run fractionally faster, but it is very unstable. Switching to 8MHz to keep it all happy is the way to go, but still ends up being slower than it really should be. So neither method is a "good" option.

Another issue is that we have the ACIA timings to complicate things even more, the CPU has to down clock to 8MHz.. But this is why I like the SEC CPU, as you have to emulate those timings yourself manually, but these are free running that no switching about frequencies is needed at all. So makes a design a whole lot better.

Of course in terms of future booster designs, the ROM decoding will be done by the PLD logic all in the faster clock domain, so these problems would not be apparent on a proper booster like the STFM V2.2. This STE booster really needs its own ROM and SEC CPU, but that's more work and expense.. I'm not really happy about how these STE boosters are coming together, but again, I just don't have time to build a "proper" full blown booster for the STE. I don't even have time to do the STFM one!

It is why I just think all this time is better spent on developing a new ST machine and new hardware to fit it. I have gone through all this development work countless times with various boosters over the years, I dare say 90% of the time is fighting problems which should not be there in the first place. As said before, it is just not a constructive use of time... While it is more work initially to create a new motherboard, upgrades for it will ultimately take considerably less time to develop.

</rant>

[PhilC]

#MongrelBoard

[exxos]

Got 3 more boards working.. then the next 2 don't

Resoldered the thing like 4 times, makes no odds.. and yet I checked all the CPU pins were connected and no shorts before soldering the pins and GAL into place , pretty annoying, I mean its getting to like 50% failure rate and no idea why

Though I got the revised PCB layouts yesterday, so will try and build a few of those up and see if I have better luck..


Exciting stuff below!





I did look at live steaming, but then it was moaning my cam was in use (which it wasn't) then turns out need to install some software, to which spent half hour going around in circles, then started to watch a video on how to set it up, which was goto some other site to download software, where I have to register.. so at that point was "oh forget it" and that's as far as it went. #nopatience.

[PhilC]

Interesting video. Always makes me wonder when you apply more solder and the pad still doesn't look any better coated. Are those holes played through? I had a number of issues lately due to soldering too quickly and Not allowing the solder to flow through the board layers.

That and you need a new soldering iron tip. Will go buy something from the store so you can afford one.

[exxos]

They are all Via's.

My tip is actually a new one, they go black so fast its terrible. I mean the weller irons and tips we used to use in my old workplace never used to need to change them. I need a new iron and some quality tips