off topic - capatob - saratov2 computer Russsian pdp8? HELP
Guy Sotomayor Jr
ggs at shiresoft.com
Sun Jan 6 12:25:53 CST 2019
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 at 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
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