It will also depend what you mean by "fastest" eg. fastest control/data transfer rate (communication interface mode), fastest read, fastest write (will also depend on the type of read/write AIUI). For example it's been discovered that the "overall performance" of (some) "faster" A2 cards can be worse than "slower" A1's. Why do you wish to "buy the fastest" (or what do you think you'd gain by doing so)? For most folks "best value" Gb/buck" is likely to be more important (or, to put it another way, there are other potential "bottlenecks" in overall performance of a Pi ...) And remember, the uSDHC card is not the only storage device and for quite a lot of the time a Pi will not be reading or writing to/from it ie. processing will be RAM-based (much faster).spaceman5 wrote: ↑Mon Aug 26, 2019 4:29 pmI understand.
The purpose of my question, is to buy the fastest microSD card that RPi 4B supports,
but not faster than that.
A faster card than RPi's max speed will work, as you say,
but will cost much more, yet this extra speed will not be utilized..
So for this reason, it will help to know what the SoC can get to..
In my experience, the difference in price is almost quite literally, pennies.
Between the Sandisk Ultra (White) and Sandisk Ultra (Red) - A1, you are right, the difference is negligible.
A nice table that summarizes A1 and A2 specification:
Amazing,fruitoftheloom wrote: ↑Tue Aug 27, 2019 4:47 amhttp://www.pidramble.com/wiki/benchmarks/microsd-cards