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What type MMU for Atari 1040 stfm 2meg hack?


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#1 Sir Les OFFLINE  

Sir Les

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Posted Tue Jul 31, 2012 11:42 AM

Hello
I have a old Atari 1040stfm system , which has been preserved in a vault for over 20 years.
Back then I started a hack to upgrade the memory to 2megs, and got the chips removed from the board, and new sticks installed.

The system works still, but it does not see the other meg of memory.
I lost all the hack instructions...but was told back then I might have to replace the MMU chip...

Anyone here know anything about that kinda stuff?...Are there any docs on doing this around still?...and or where I can still buy parts to update this machine...?

I would also like to put in a new IDE floppy if that is possible....and I know there was a hack for that back then aswell...any help would be appreciated...

Thanks

#2 ParanoidLittleMan OFFLINE  

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Posted Wed Aug 1, 2012 2:50 AM

I don't know about MMU type not supporting 2MB of RAM. IMP brand supports not 2.5 MB (will see only 2 then) - that's what I expereienced. I guess that problem is somewhere else.

Ops. You can not expand from 1MB to 2MB just like that. 1MB uses both banks. Only way is to replace whole RAM with 1Mb chips (instead 256Kb ones). It may be done by leaving original chips in board, but deactivationg them by connecting all CAS/RAS/WR lines to high. And adding board with 2MB RAM - but max 16 chips total. I have one.

Considering IDE for 1040/520 ST: http://atari.8bitchip.info/aidesch.htm

#3 Sir Les OFFLINE  

Sir Les

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Posted Wed Aug 1, 2012 7:42 AM

I don't know about MMU type not supporting 2MB of RAM. IMP brand supports not 2.5 MB (will see only 2 then) - that's what I expereienced. I guess that problem is somewhere else.

Ops. You can not expand from 1MB to 2MB just like that. 1MB uses both banks. Only way is to replace whole RAM with 1Mb chips (instead 256Kb ones). It may be done by leaving original chips in board, but deactivationg them by connecting all CAS/RAS/WR lines to high. And adding board with 2MB RAM - but max 16 chips total. I have one.

Considering IDE for 1040/520 ST: http://atari.8bitchip.info/aidesch.htm


Thanks for the link and info.
I removed the original chips completely , as instructed by the hack way back then, and no longer have them to put back....and ran lines to the new sticks...When I boot the system up now, only 1meg is seen...I know it might be something to do with the MMU chip, being only able to register the 1 meg...as this has stayed in my head, as being told on a forum back then...if it does not see the 2megs then you have to swap out the MMU for a newer one that registers 2meg and above.
Now as I believe if my soldering was bad, on one stick or the other, the system would not recognize any....So as it is seeing 1 meg, I know my work so far is sound...or am i decieved in believing that?

#4 ParanoidLittleMan OFFLINE  

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Posted Wed Aug 1, 2012 9:28 AM

Old MMUs work fine with 2 or 4MB. I had couple 520 STs, and all worked with 2MB RAM well.
Check again all your connections, solderings. And possible too that some chip is faulty.
Or you soldered bad some adress line.
Of course, it is easier to replace MMU chip - but I bet that error is somewhere else. And you need to buy that chip.

#5 Sir Les OFFLINE  

Sir Les

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Posted Thu Aug 2, 2012 6:39 AM

Old MMUs work fine with 2 or 4MB. I had couple 520 STs, and all worked with 2MB RAM well.
Check again all your connections, solderings. And possible too that some chip is faulty.
Or you soldered bad some adress line.
Of course, it is easier to replace MMU chip - but I bet that error is somewhere else. And you need to buy that chip.


Ok..I will check that work I did out more closely,...kinda hard to know, what is what, now, with out any docs to follow...know any good sources for any more Memory updates for the Atari 1040stfm?..so I can undertake this again?

Thanks for the help and link ..


Blessings!

Sir Les

#6 ParanoidLittleMan OFFLINE  

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Posted Thu Aug 2, 2012 8:10 AM

http://dev-docs.atariforge.org/

And google is at hand too :)

I did all in past without Internet - only using Atari ProfiBuch and some memory documentations.




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