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Are "1TB" micro-SD cards 1000GB or 1024GB?
Frankenpod:
I've been experimenting with how close one can get to the 2TiB limit (using the iFlash quads in ipods) and am confused by the results I've gotten.
Based on previous results I _had_ concluded that so-called "1TB" cards are actually 1000GB - which would seem to be consistent with how storage media are labelled using the "SI" prefixes, based on factors of 1000, rather than the 1024 multiples computing usually uses (hence the distinction between GB/TB and GiB/TiB etc).
But when I tried a combo of two 1TB cards, a 128GB and a 64GB, it came out, when restored, as 36GB. To me that seems consistent with the 1TB cards actually being 1024GB, which would mean the total adds up to 2240GB, which is about 2086GiB, so about 38GiB over the maximum 2048GiB. Had the 1TB cards been 1000GB the total would have been 2192GB, i.e. 2042GiB, which should have worked as it's under 2048GiB.
(With the 64GB excluded card it worked, but in the end rearranged things entirely to make two separate ipods each with 1TB 512 512 128 combo, which always seems to work)
So are 1TB cards actually 1024GB? That seems a bit weird to me, given that in general the card manufacturers seem to use the decimal definitions of the prefixes. Is it possible some manufacturers' 1TB cards are 1000GB but others give you the 'full' 1024GB?
gevaerts:
My guess is that "it depends on the manufacturer" is the correct answer.
That said, trying to get exact card sizes by trying out combinations of them and seeing what they add up to feels like the hardest way to do it. I'd just put them in a card reader and see what they actually report as.
Frankenpod:
Yeah, you're right, that just looking at them in a card-reader would (have been) the way to go.
Just didn't really think about the question beforehand, because I'd concluded (judging from how these ipods turned out before with various card-combos) that 1TB must be 1000GB, but then found that (1000,1000,128,64) combo didn't work, and can't really check the issue after-the-fact as the cards are now all in assembled-and-synched ipods (that I'm not dismantling again!).
Think I'll take as a working assumption that different manufacturer/brands define 1TB differently. Haven't seen any results from anyone checking them, though.
[edit] There seems to be no consistent relationship between the 'nominal' capacity of the four-card combo based on the claimed card sizes, and the capacity you eventually get. E.g. for ipods I have using (1TB 512 512 128), (with a hotch-potch of different card brands) the eventual size reported by rockbox for them ranges between 1989GiB and 2024GiB
speachy:
--- Quote from: Frankenpod on May 20, 2025, 01:30:57 PM ---Think I'll take as a working assumption that different manufacturer/brands define 1TB differently. Haven't seen any results from anyone checking them, though.
--- End quote ---
I would be *shocked* if any SD card was anything other SI prefixed. The storage business has been nearly entirely SI-prefixed for what, 40+ years now?
(The only general exceptions I'm aware of are old floppy drives and CDs, those used MiB. Hard drives and DVDs have always been SI units)
FWIW, I have a card labeled as "16MB" card that is actually only 14.9MB (or 14.2 MiB), similarly an "8GB" card reports as 7.95GB/7.40GiB.
So clearly that capacity on the label is only nominal, precise capacity can and will vary. But I can promise you it's going to be SI units either way.
Frankenpod:
Thanks for that information. So the issue is more likely to be just cards not being quite the capacity they claim to be, even if they are in theory using SI units? I don't really know anything about the topic of memory-card-manufacturing, is there a degree of random variation in exact sizing? (leaving aside the issue of outright fakes). Seems as if somehow the cards in this instance were a tiny bit _larger_ than claimed.
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