It depends on the program, how much data you're writing (cache size), and the speed of the storage relative to the data you're writing. For example, if I have a trivial program that adds an infinite amount of 64-bit integers together, it's clear that the program will run faster if compiled to take advantage of a 64-bit processor (instead of using the 32-bit counterpart instructions). However, the work done is trivial, and the CPU can add numbers together much faster than you can store them onto an HDD/SSD (thus filling up the cache on the disk drive, limiting the operation to the storage speed).
However, if we look at the operations done by the CPU, we can see that the 32-bit version will take longer to complete, only performing work and copying 32 bits of memory at a time to the cache controller (with the use of direct memory access (DMA)). In this case, the 64-bit operation might theoretically fill the disk's cache controller more quickly for burst operations, it's more likely that in both cases, the cache would be filled and the operation speed would be limited mostly by the write speed of the disk itself.
3It doesn't affect the read/write speed. – ChrisInEdmonton – 2014-12-17T16:54:08.927
You might read Hard Disk Speed - What Affects Hard Disk Performance? on a little bit of a background on what can address read/write disk speeds.
– scrappedcola – 2014-12-17T17:10:21.5201Why would the size of a x86 register effect the I/O speed of a hdd? Doing an I/O read/write at the point the read/write is done has very little to do with those registers. – Ramhound – 2014-12-17T17:10:38.727
I don't know, that is my question. How does it affect the I/O speed of a had? – dev gr – 2014-12-17T17:13:31.503
3Just because the answer is obvious to some of us doesn't mean the question is invalid or off-topic. – nhinkle – 2014-12-17T17:18:19.577
Was it the only purpose of 64 bit processor to be able to address more main memory? – dev gr – 2014-12-17T17:19:33.820