Possible problem with cloned SGC and Minerva 1.98

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MartynHill
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by MartynHill »

That is interesting...

I shall try my cloned SGC in an Iss5 as another test - I had been wondering whether the ZX8302 sitting one side of the DRAM bus or the other might also be contributing to the issue (timing accessing the PC would be slightly different, I believe.)


martyn_hill
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by martyn_hill »

OK, no difference in behaviour with the SGC in my Iss5.

Looking more and more like the SGC ROM version...


RWAP
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by RWAP »

I thought the 2.32 ROM was from a Gold Card - could it be the difference between the Gold Card and the Super Gold Card (ie 68000 chip and 68020 chip) ?


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mk79
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by mk79 »

OK, I badly need to go to bed, but just as a heads up, I found it, it's a bug in Minerva. Details to follow.


martyn_hill
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by martyn_hill »

OOoOOooO!

I'm excited for your next installment, Marcel!


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mk79
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by mk79 »

That's good to hear, because here it is ;)
https://www.kilgus.net/2018/11/16/microdrive-mystery/

I made it in form of a quiz, so you have a last change to spot the bug yourself, don't scroll too far for the solution :-P


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Re: Possible problem with cloned SGC and Minerva 1.98

Post by RWAP »

Thanks Marcel - once you had shown the code I spotted the problem.

Rather than updating Minerva, is the solution to update the Gold Card / Super Gold Card ROMs to use:

Code: Select all

        moveq #0,d0
        move.w gmt_fgap,d0              ; 2800 us
        dbra    d0,*
Then you don't need to worry about the Minerva ROM version number - I guess it depends how much spare room is in the (S)GC ROMs...


martyn_hill
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by martyn_hill »

Well, thanks Marcel!

I have recompiled Minerva with the tiny change Marcel describes in his blog to the Scatter-load routine in mdvsc_asm and can confirm that LBYTES now works again on Min 1.98!

Amazing bit of detective work - I am in admiration!

It remains to be seen whether we should rev. Minerva or else the SGC ROM, but for now I'm happy!


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mk79
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by mk79 »

RWAP wrote:Thanks Marcel - once you had shown the code I spotted the problem.

Rather than updating Minerva, is the solution to update the Gold Card / Super Gold Card ROMs to use:
Yes, that is of course an option, albeit not my preferred one. So far nobody changes (S)GC ROMs while I send new Minervas into the world with QL-SD, so fixing it in Minerva is my main priority. Eventually I want to release a new (S)GC ROM with a few enhancements anyway so this could be incorporated, but that will take some more time.

Marcel


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Cristian
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Re: Possible problem with cloned SGC and Minerva 1.98

Post by Cristian »

Immunizing SGC against Minerva bug(s) may make sense... provided that we don't introduce new bugs, obviously.
Anyway, I think it's more correct to fix Minerva above all.


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