The MIPS, PowerPC and SPARC all grew to 64 bits from 32 bits, so 32 bit quantities (and usually but not always 16 bit and 8 bit quantities) have suitable instructions to fetch them. Exceptions include ARM, where the original 32 bit architecture made byte access (in the C style at least) expensive, but they corrected that in (I think) v4 by adding byte instructions. Alpha might have been an exception too, but that's dead.
accesses aren't "unaligned" when they are smaller than the machine word, but when the address isn't a multiple of the length accessed. Plan 9 generally keeps things properly aligned. Processors don't usually have trouble with accesses smaller than the machine word. On 7 May 2012 11:01, dexen deVries <dexen.devr...@gmail.com> wrote: > on RISC, there's usually significant penalty for accessing data units > smaller > than machine word (`unaligned access'), but it ain't so on the benevolent > x86 > CISC. >
