Mega ST project

General discussions or ideas about hardware.
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frank.lukas
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Re: Mega ST project

Post by frank.lukas »

for a test remove the STORM card and see if it makes a difference ...
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HigashiJun
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Re: Mega ST project

Post by HigashiJun »

I will have to run the STGA drivers from floppy then, as my STORM ST is also a TOS board decoder for my 2.06 TOS...

I should have time tomorrow to perform the test though.
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Darklord
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Re: Mega ST project

Post by Darklord »

Oh, you're not using the Pak modified version of TOS v3.06?

May I ask why or why not? Just curious. :)

PS Just jumped back to the original post - I had missed where
you mentioned TOS v2.06 - apologies.
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HigashiJun
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Re: Mega ST project

Post by HigashiJun »

I won't need the TOS decoder anyway, as I want to check how my PAK68 performs with the STGA, so the fallback mode is not necessary here...
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HigashiJun
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Re: Mega ST project

Post by HigashiJun »

frank.lukas wrote: Mon Jan 03, 2022 7:12 am for a test remove the STORM card and see if it makes a difference ...
Just tried without the Storm ST and the result is still the same...

I have also found in the VOFA documentation (with the help of an online translator) that this card could cause issues with PAKs.

They advise to add 300 Ohm resistors between Vcc and R/W and, if it does not help, also add a 1K resistor between Vcc and DTACK.

Would it be a solution for the STGA ?
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HigashiJun
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Re: Mega ST project

Post by HigashiJun »

Tried the resistors trick found in the VOFA documentation but nothing changes. :evil:

My Mega ST is still stopping at the driver info screen.

Hope to make all the stuff work sooner or later though.
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HigashiJun
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Re: Mega ST project

Post by HigashiJun »

OK, finally got it working.

Everything runs now (though still needs some tweaking) but only with my previous VGA board.

I cleaned thoroughly all the ISA contacts, plugged the VGA and had an output on my monitor.

The smaller VGA card does not want to run with the PAK68 fitted, even after its contacts have been cleaned.

Is it due to the fact it has a GENDAC instead of a RAMDAC ?

Though RAMDACs are not supposed to work with VOFA nor STGA, this board works when the PAK68 is removed.

I guess Frank Lukas might have an opinion on this matter.

Mega.jpeg
Mega.jpeg (408.81 KiB) Viewed 2069 times
Bench.jpeg
Bench.jpeg (282.84 KiB) Viewed 2069 times

Would have prefer the smaller board, as I could close my Mega ST without cutting the case...
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HigashiJun
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Re: Mega ST project

Post by HigashiJun »

Had more time this morning to try my VGA cards.

The bulkier one works nicely in fallback mode at 8 Mhz and works also at 40 Mhz, but there are artifacts on the screen.

The smaller one now works at 8 Mhz but does not want to go further than the driver screen at 40Mhz.

The Mega ST journey is not over yet...
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HigashiJun
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Re: Mega ST project

Post by HigashiJun »

Swapped for a 32 Mhz crystal on the PAK68 and no more artefacts.

Will have to investigate more, as the PAK is surely capable of a tad more than 40 Mhz without a PUPLA (unfortunately not 50 Mhz...).

Only the VGA is a bit problematic at 40 Mhz.
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Darklord
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Re: Mega ST project

Post by Darklord »

Is a PuPla required for 50mhz? I did not know this...
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