Fun fact: people like to say that unlike Flash memory, RAM can be read or written to one byte at a time, but that's a lie. A typical DIMM's memory array can only be addressed in 64KiB blocks! Writing one byte means reading 64K, modifying one byte, and writing 64K! (1/n)
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In fact, *reading* is a destructive operation in RAM. Reading one byte means reading 64K (which destroys it), then writing back the 64K untouched! However, the RAM chips perform this read-write operation when directed, so the 64K doesn't have to go out via the bus and back. (2/n)
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Replying to @marcan42
Wait, so does this mean this all happens 64K times when you do write/read an entire block of memory? And even multiple times when the CPU reads or writes a cache line etc? Or is there a way around that?
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No, the RAM can batch a series of operations on the same block together so it gets read once, updated, and written back again once it's all done. Cache lines in particular would pretty much always be read or written as a single operation, never split.
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