Specifications set minimum requirements, rarely does a specification set an actual maximum limit.
In this case, the specification requires that compliant hardware support *at least* the rates specified (within the defined optionality of the specification), but does not bar hardware from supporting higher rates or additional features, as long as the specification is met otherwise.
Most likely the manufacturer is quoting the maximum possible rate for their hardware under laboratory conditions and using carefully specified supporting hardware; rather than the real world conditions with various unknown additional hardware elements (e.g. a card reader) and environmental conditions.
Basically, you'll probably never see the maximum quoted data rate because some *other* hardware in the system probably won't support it (again, readers *can* support higher speeds, but most won't), but the card *could* deliver data at those rates in a theoretical perfect environment.
Most quoted rates do, somewhere in fine print and often only on their website, describe the basis for the claim.  With a little digging you can probably find the exact answer if you're curious enough.


On 2022-12-01 02:22 PM, Jim via PLUG-discuss wrote:
> I know this isn't really a linux question, but I don't know who else to ask and I haven't yet found an answer online, but I'm still looking.
> 
> I'm looking at buying a micro sd card and have found some UHS -I cards that advertize 180 MB/s read speeds and 130 MB/s write speeds,  I've also read that UHS - I is supposed to have a maximum speed of 104 MB/s.  Are the card makers guilty of false advertizing, or is there some way to get around the 104 MB/s limit?
> 
> 
> thanks
> 
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