Macintosh SE Sad Mac: Bad RAM chip identification possible?

JDW

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I've been testing my inventory of 1MB RAM SIMMs using my Mac SE Reloaded machine, and with one particular set of SIMMs, I get a Sad Mac at cold boot showing these 2 lines:

00000004 <— "Bank A"
00004000 <— Failed bits...

AABBCCDD​
AA = bits 31-24
BB = bits 23-16
CC = bits 15-8
DD = bits 7-0​

1659869828472.png

Failed SIMM (8 Chips marked SANYO LC321000J-10):

tempImage4pC3tW.png

1659870753010.png

There's another SIMM just like it which tests fine when used with my known good RAM. So it's not a matter of that particular RAM type not working in an SE.

QUESTION: As per the above, can it be determined which IC or ICs are in need of replacement?
 
Solution
So, if you re-read what i was saying - the faulty one will be in SIMM SLOT 2. You could get a SIMCHECK unit, or something similar - however, the only way you can really test without one, is 'in-situ' using an oscilloscope. If you probe the data and address lines you should be able to see which line one is acting weird, but that only narrows down WHAT is going wrong. You'd need to test each chip on the SIMM individually to really test it further.

I did come across this though: https://hackaday.com/2014/04/09/using-simms-to-add-some-extra-ram-on-your-arduino-uno/

That might be a basis for constructing a tester. Alternatively, I'd lend out my Innoventions SIMCHECK to someone like @Zane Kaminski if there was interest in...

JDW

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JDW

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Well, how about seeing if you can find that IC? Unobtainium? :sneaky:
It might be possible to find. It's just not high priority for me right now since I have other good and working 1MB SIMMs. But I can come back to this at anytime, get a new chip and see if that works.

Pretty amazing animated GIF you made there! That must have taken some serious time to create! But please know that @YMK deserves all the credit. By the way, if you don't already have a MacSD, you ought to give one a try.
 
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retr01

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I can come back to this at anytime, get a new chip and see if that works.

That'd be cool! :cool:

Pretty amazing animated GIF you made there! That must have taken some serious time to create! But please know that @YMK deserves all the credit.

Thank you! 😊 It does take serious concentration and effort, yes. Sometimes quick. Other times, not. Depends on the circumstances and work involved.

Oh definitely! @YMK deserves all the credit for the fabulous idea and for helping you, @JDW. 👏 I want to point out that many things I noticed we do here on TinkerDifferent are a group team effort, too. Everyone contributes in some way. 🤝

What do you think, @YMK? Did you like the animation? :D

By the way, if you don't already have a MacSD, you ought to give one a try.

Yes, @YMK's MacSD is on my list. :)✍️

1660059431808.png
 
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