exxos's Atari, Amiga & retro forum

exxos wrote: 02 Oct 2021 08:18 The mega ST is the worst machine to update. All you can do is the mandatory fixes. Beyond that, you're fighting an unstable bus. Debugging will take a lot of time. It's why I don't support mega anymore. STFM is hard enough. It's why I designed the remake boards. If you *really* want it to work, then get a fast logic analyser like @terriblefire has and start to debug the entire bus to see where the issue is.

Yes, you are completely right Exxos... The STE was a real piece of cake to upgrade compared to the Mega ST.

I will try to get a Logic Analyser if the Mega starts to seriously get on my nerves. And if nothing helps, I will not fit the PAK68 (thus the relocator) as all other upgrades work great without the relocator or I will take a hammer and :chairsmack: this moron.

I updated my previous post. But also, if you have a SR98 PSU, recapped of course, lower the voltage to say 4.8v and see if things improve. You are fighting noise and bad PCB grounding, swapping CPU relocators is not the answer..

exxos wrote: 02 Oct 2021 08:51 I updated my previous post. But also, if you have a SR98 PSU, recapped of course, lower the voltage to say 4.8v and see if things improve. You are fighting noise and bad PCB grounding, swapping CPU relocators is not the answer..

I will try that ASAP.

Thanks Exxos !

I had not really much time today to try Exxos' suggestions, so I only removed the CPU relocator and packed the Mega ST with Alt-RAM, Lightning ST and the STGA.

I have also fitted my STPSU just in case.


And... everything works great and is rock solid, even after some Gembench tests.

(The VGA is not configured yet, thus the non-centered screen).

So my conclusion is: the relocator is the culprit causing the bombings and freezings.

It is quite weird that this simple PCB board can f..k-.p a whole configuration, making it unstable. :o

Will do some more tests as soon as I can...

HigashiJun wrote: 04 Oct 2021 13:21 So my conclusion is: the relocator is the culprit causing the bombings and freezings.

It is quite weird that this simple PCB board can f..k-.p a whole configuration, making it unstable. :o

Yep. I run into that problem during the V2.2 booster series. There was many many posts about this some years ago. I had one design working perfectly well, and I revise the PCB slightly and it never worked since. I even removed all booster parts so it was just literally a DIP to PLCC CPU adapter. This is why it is important to have properly designed PCBs and do the mandatory fixes.

exxos wrote: 04 Oct 2021 13:29

HigashiJun wrote: 04 Oct 2021 13:21 So my conclusion is: the relocator is the culprit causing the bombings and freezings.

It is quite weird that this simple PCB board can f..k-.p a whole configuration, making it unstable. :o

Yep. I run into that problem during the V2.2 booster series. There was many many posts about this some years ago. I had one design working perfectly well, and I revise the PCB slightly and it never worked since. I even removed all booster parts so it was just literally a DIP to PLCC CPU adapter. This is why it is important to have properly designed PCBs and do the mandatory fixes.

Well, that is good to hear... I thought I was the only guy here having such weird issues. :lol:

But I cannot blame Frank Lukas, who kindly sent me for free the first version of his relocator and then the Gerbers for its second version.

Thank you Frank, and I hope you are more lucky than me with your add-on.

:thanksyellow:

Something weird...

I tried another CPU relocator in my Mega ST and I had a no-go as well: RAM errors, instabilities and so on...

When I tried my 2 relocators in a friend's Mega ST, everything was OK and issue free.

So my Mega ST becomes unstable with a relocator fitted and goes back to normal once the relocator removed and all the other expansions installed.

:evil:

Removing my suggestion... do mandatory fixes and also see what frank says too

AFAIK he's not done the mandatory fixes yet. As mentioned some time ago, randomly swapping stuff isn't the answer. Swapping to 74F series on a mega is asking for trouble.

HigashiJun wrote: 13 Oct 2021 13:46 Something weird...

I tried another CPU relocator in my Mega ST and I had a no-go as well: RAM errors, instabilities and so on...

When I tried my 2 relocators in a friend's Mega ST, everything was OK and issue free.

So my Mega ST becomes unstable with a relocator fitted and goes back to normal once the relocator removed and all the other expansions installed.

:evil:

Try to add 10K Pullup SIL resistors to the Data Line D0-D15 and 4,7K SIL resistors to the Address Lines direct on to the relocator CPU socket pins. LS244/373 can maybe swap to 74ALS ...