I think it’s also telling that the IETF uses the term octet in all of the specifications to refer to 8-bit sized data. As “byte” (from older machines) could be anything and is thus somewhat ambiguous.
It *may* have been the IBM 360 that started the trend of Byte == 8-bits as the 360’s memory (in IBM’s terms) was byte addressable and the instructions for accessing them were “byte” instructions (as opposed to half-word and word instructions). TTFN - Guy > On Jan 6, 2019, at 10:19 AM, Noel Chiappa via cctalk <cctalk@classiccmp.org> > wrote: > >> From: Grant Taylor > >> Is "byte" the correct term for 6-bits? I thought a "byte" had always >> been 8-bits. > > I don't claim wide familiary with architectural jargon from the early days, > but the PDP-10 at least (I don't know about other prominent 36-bit machines > such as the IBM 7094/etc, and the GE 635/645) supported 'bytes' of any size, > with 'byte pointers' used in a couple of instructions which could extract and > deposit 'bytes' from a word; the pointers specified the starting bit, and the > width of the 'byte'. These were used for both SIXBIT (an early character > encoding), and ASCII (7-bit bytes, 5 per word, with one bit left over). > >> I would have blindly substituted "word" in place of "byte" except for >> the fact that you subsequently say "12-bit words". I don't know if >> "words" is parallel on purpose, as in representing a quantity of two >> 6-bit word. > > I think 'word' was usually used to describe the instruction size (although > some machines also supported 'half-word' instructions), and also the > machine's 'ordinary' length - e.g. for the accumulator(s), the quantum of > data transfer to/from memory, etc. Not necessarily memory addresses, mind - > on the PDP-10, those were 18 bits (i.e. half-word) - although the smallest > thing _named_ by a memory addresses was usually a word. > > Noel
