Mega ST project

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HigashiJun
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Re: Mega ST project

Post by HigashiJun » Sat Oct 02, 2021 8:47 am

exxos wrote:
Sat Oct 02, 2021 8:18 am
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.

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exxos
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Re: Mega ST project

Post by exxos » Sat Oct 02, 2021 8:51 am

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..
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~

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HigashiJun
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Re: Mega ST project

Post by HigashiJun » Sat Oct 02, 2021 8:59 am

exxos wrote:
Sat Oct 02, 2021 8:51 am
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 !

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HigashiJun
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Re: Mega ST project

Post by HigashiJun » Mon Oct 04, 2021 1:21 pm

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 Centuriontech STPSU just in case.

MegaST.jpeg
MegaST.jpeg (388.19 KiB) Viewed 234 times
MegaSTvga.jpeg
MegaSTvga.jpeg (379.02 KiB) Viewed 234 times

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...

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exxos
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Re: Mega ST project

Post by exxos » Mon Oct 04, 2021 1:29 pm

HigashiJun wrote:
Mon Oct 04, 2021 1:21 pm
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.
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~

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HigashiJun
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Re: Mega ST project

Post by HigashiJun » Mon Oct 04, 2021 1:41 pm

exxos wrote:
Mon Oct 04, 2021 1:29 pm
HigashiJun wrote:
Mon Oct 04, 2021 1:21 pm
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:

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HigashiJun
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Re: Mega ST project

Post by HigashiJun » Wed Oct 13, 2021 1:46 pm

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:

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Steve
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Re: Mega ST project

Post by Steve » Wed Oct 13, 2021 3:55 pm

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

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Re: Mega ST project

Post by exxos » Wed Oct 13, 2021 4:12 pm

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.
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~

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frank.lukas
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Re: Mega ST project

Post by frank.lukas » Wed Oct 13, 2021 5:13 pm

HigashiJun wrote:
Wed Oct 13, 2021 1:46 pm
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 ...

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