Byte sizes (was Re: 2.8M 3.5' floppy (was: three and a quarter loppy?)

[Paul Koning]

>>>>> "der" == der Mouse <mouse at rodents.montreal.qc.ca> writes:

 >> Also, the MC68000 has bit-manipulation instructions that can
 >> address individual bits, but it is not considered to have one-bit
 >> bytes.

 der> ...The description
 der> of the -10 as I read it implied that there was a single object,
 der> defined by the hardware, which encapsulated the word address,
 der> bit number, and size, which sounds way too much like a bit
 der> address.  ...

I believe that's right.

For that matter, the Burroughs 6800 has a somewhat similar mechanism
(characters as a subsidiary datatype with hardware-defined character
pointers). 

In both cases, you have a construct that consists of a word address
and a byte-in-word address.  So the part that describes the byte
describes it as a piece of a given word, which is addressed by another
part of the composite pointer.  That's why those are still considered
word addressed machines (36 and 48, respectively) -- the ability to
pick a character out of the word is viewed as a secondary operation
distinct from the primary memory addressing.

	 paul