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Atari MEGA 1 RAM upgrade


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#1 candle OFFLINE  

candle

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Posted Thu Dec 31, 2009 11:47 AM

Hello everyone, Happy New Year ;)
I've bought myself Atari MEGA 1 recently, and decided to do something creative with it ;)

Here are the results:

Posted Image
For start, we need to desolder old RAM chips - its not an easy task, since all of them are SMT chips - You could probably cut them out, but this will be a point of no return ;)
I use HOT AIR SMD REWORK soldering station

Posted Image
After desoldering the chips, old solder remains on SMD pads, we need to get rid of it, because it will prevent us from soldering new chips properly
For this i recommend using solder wick

Soldering of new chips is not that hard as it might seem, just use fine tip solder iron, and precisly place the chip on pads before soldering it - there is verry little margin for error here

Posted Image
Throught the PCB we need to drill a hole (or use one of existing ones) and conduct the wire from pin #5 of first RAM chip (U40) to pin #64 of MMU (U30)

Posted Image
What we need to do now, is to connect all pin #5 of RAM chips together forming MA9 line that makes this upgrade complete

required chips can be found on 30 pin SIMM modules, the same as we use for 8bit Atari memory upgrades

Candle

#2 tjlazer OFFLINE  

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Posted Sat Jan 2, 2010 3:10 AM

Very nice work! If I lived close I would have you do an upgrade to my Mega 2. ;)

#3 candle OFFLINE  

candle

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Posted Sat Jan 2, 2010 7:27 AM

move then ;)

#4 Lynxman OFFLINE  

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Posted Sun Jan 10, 2010 1:57 PM

I've bought myself Atari MEGA 1 recently, and decided to do something creative with it ;)


This is very nice, i have done the same with 2 or 3 Mega 1. But there are some Mega 1 which are made with DIL-DRAM-chips...
You made very good pictures, no problem for other people to do the same. :thumbsup:

What we need to do now, is to connect all pin #5 of RAM chips together forming MA9 line that makes this upgrade complete


Do you use a 68 Ohm resistor? Atari uses this resistors in the MAD-lines to the memory chips.

required chips can be found on 30 pin SIMM modules, the same as we use for 8bit Atari memory upgrades


And this chips can also be found at Lynxman. :cool: New, unused, best quality (Mitsubishi or Motorola 60/70ns) for 2 (8chips for only 2!) + shipping.
So there is no need to desolder the chips.

Very nice work! If I lived close I would have you do an upgrade to my Mega 2. ;)


Was there ever a Mega 2 with SMD-memory-chips?

Lynxman

#5 candle OFFLINE  

candle

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Posted Sun Jan 10, 2010 2:43 PM

i haven't noticed any terminators on MA lines, perhaps i was not paying enought attention
never the less upgrade runs perfectly stable

#6 Lynxman OFFLINE  

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Posted Tue Jan 12, 2010 4:01 PM

i haven't noticed any terminators on MA lines, perhaps i was not paying enought attention
never the less upgrade runs perfectly stable


You can see this Resistors in your first pic. Starting with R52.

Anyway, your Mega is working.

#7 candle OFFLINE  

candle

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Posted Tue Jan 12, 2010 5:01 PM

and i can also see they are rated for 33R ;)

#8 Lynxman OFFLINE  

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Posted Sat Jan 16, 2010 7:56 AM

and i can also see they are rated for 33R ;)


OK, you are right. I think the 68R was used for /RAS and /CAS.

#9 qq1975b OFFLINE  

qq1975b

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Posted Tue Feb 24, 2015 6:08 AM

So...was the 68R needed? or only replacing the DRAM chips and linking them as described is OK?



#10 guus.assmann OFFLINE  

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Posted Tue Feb 24, 2015 10:49 AM

For RA9 a 33 Ohm resistor is needed.
This will reduce spike signals when accessing the chips.
So less noise and more reliable operation.

BG/
Guus

#11 exxosuk OFFLINE  

exxosuk

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Posted Tue Feb 24, 2015 12:25 PM

Nice work :)  I don't suppose you could post a high-res top view of the motherboard ?  I am working on some MEGA related problems and not seen the SMT RAM version of that board yet :)



#12 Tillek OFFLINE  

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Posted Wed Feb 25, 2015 2:59 AM

Just out of curiosity, did this take it to 4mb, or something else?



#13 qq1975b OFFLINE  

qq1975b

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Posted Wed Feb 25, 2015 3:07 AM

4 MB






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