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Identifying a defective RAM IC on laptops with soldered memory

Identifying a defective RAM IC on laptops with soldered memory

5 comments

·April 2, 2025
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Retr0id

By the way, the reason the address->IC mapping is non-trivial is for performance reasons.

If you were, for example, iterating over a column of a 2D array with a stride equal to some power of two, you'd end up hitting the same IC repeatedly. This limits your bandwidth to that of a single IC, rather than balancing it over all of them. (I'm simplifying a little, but that's the gist)

So they try to "swizzle" things, using a formula like the one in the article.

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[deleted]

Luc

Not loading for me, but here's the archive: https://web.archive.org/web/20250207044221/https://blog.pier...

On 80's arcade games and home computers you can try piggybacking a known working RAM chip onto each of the RAMs for a quick diagnosis, if you're lucky (it doesn't always work).

harshreality

If you stress test small address ranges around each failing address, does that selectively heat up the chip to which that address routes?

Then all you'd need is an infrared imager.

mrob

Alternatively, could you stress test the failing addresses while selectively heating each chip in turn with a hot air gun and checking if the error rate changes?