Atari MEGA 1 RAM upgrade

[candle]

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:

 

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

 

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

 

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)

 

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

[tjlazer]

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

[candle]

move then

[Lynxman]

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.

 

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. 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

[candle]

i haven't noticed any terminators on MA lines, perhaps i was not paying enought attention

never the less upgrade runs perfectly stable

[Lynxman]

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.

[candle]

and i can also see they are rated for 33R

[Lynxman]

and i can also see they are rated for 33R

 

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

[qq1975b]

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

[guus.assmann]

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

[exxosuk]

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

[+Tillek]

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

[qq1975b]

4 MB

[santosp]

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

 

Original TC514256AJ-10, which replaced with TMS44400DJ-70