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From “Commodore SR8120 (aka SR8120D)”?

“”“

The two GHU chips are made of a (high silicate?) epoxy I've never seen before.  
The silicate content makes chemically decapping them extremely difficult.  
Although I can get acid to penetrate a few mm to remove the epoxy it leaves 
a strong skeleton behind that so far I've only been able to remove mechanically.  
So this is where they stand:

GHU-03A: this chip has sustained enough damage now that I have to declare it "dead".  
We should get another one if its worth imaging.  I tried gradually more aggressive 
techniques to get the encapsulant off.  The last ditch effort was ultrasound which 
could work to knock the last layer off but is dangerous because on imperfect chips 
because it can cause a chip to crack...the latter happened.  I'm saving the remains 
just in case but if you *really* want this chip imaged we should get another one...
assuming I can figure out a way to decap it

”“”

Package

Die

References