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| Macintosh 128K Error Code 04feff? |
Posted by: jraust on 2017-10-27 19:09:19
I'm trying to repair my Macintosh 128K. I'm getting the error code 04feff. I read that this code can be used to figure out what RAM chip is faulty. Unfortunately, after looking at the discription, I can't figure it out. Can someone tell me what RAM chip this code points too?
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Posted by: sigtau on 2017-10-27 20:30:28
I'm working on the assumption that your 128k is not a 512k upgrade and that it doesn't have socketed chips. Now would be a good time to install sockets if you suspect more RAM may fail in the future.
I also assume that the RAM is addressed sequentially. If the chips are interlaced (i.e. chip 0 is the first bank, chip 2 is the second, chip 1 is the third, or something silly like that) someone please correct me. Correct me as well if I'm totally off base here because this is a whole load of assumptions due to me not having a 128k to compare.
8 kilobytes per chip in a stock Mac 128 (64kbits per MT4264 chip = 8 kiB). Error code byte 1 is 04 indicating it failed the mod3 test, and feff indicates the failed address 0xfeff.
For each least-significant-byte of the address, that's 128 bits. 0xffff (highest address) - 0xfeff (error address) = 0x0100 (or 256) bytes from the end of the memory map.
I would wager the last chip in the entire memory bank is bad. I think that's G12, again, someone correct me if I'm wrong.
EDIT: typo
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Posted by: BadGoldEagle on 2017-10-28 03:35:46
I don't have the necessary skills to determine which one is bad, but if I were you I'd replace all 16 chips. There's a good chance multiple chips are bad and others will definitely go bad at some point.
Charles @ Maccaps.com sells kits for $35. He replaced them on my 128k and it works great now (mine had 3 bad chips...)
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Posted by: bibilit on 2017-10-28 06:34:08
Your error code doesn't identifies bad chips.
F is for exception, but the rest is not related to anything:
https://support.apple.com/kb/TA46376?locale=fr_FR
are you turning the 128 alone (i mean only Analog and Logic board ?)
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