Anyone Ever See A Mac 128k Upgrade Like This?


macrumors 65816
Original poster
Dec 18, 2010
I picked up an original Macintosh from the original owner. It was upgraded to 512k in 1985. It's currently showing a checkerboard display, so I opened it up to take a look inside.

I've never seen a 512k upgrade that looks like this. Anyone else ever see one like this?

It also had a PRAM battery that got old and leaked onto the ROM chips on the logic board. I'm going to clean it and see if that fixes the checkerboard.

Larger photo:
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macrumors 68020
Mar 16, 2008
Australia, Perth
I haven't seen one done in that particular fashion but that's pretty much how the circuit works to add the extra address line.

AFAIK, Apple never did upgrades to 128K MLBs this way (adding the 74F253). This was the way third parties upgraded the MLB to 512K

When I did them, I had a small circuit board that had pins that fitted into the row of solder pads next to the CPU. Perhaps the method pictured would have been cheaper.

It's certainly very neatly done. :)

Looking at the ROM sockets, it might be better to get the sockets replaced.
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