Byte sizes (was Re: 2.8M 3.5' floppy

[William Donzelli]

> Well the 1620 was a variable length machine ... A sign/flag bit made 
> more sence at the time since
> you only had as many BCD digits as you needed.

It is still very inefficient, with lots of wasted bits. It would not
matter with a small machine like a 1620, but it does when the system gets
larger. Even a small S/360 dwarfs a 1620. All those wasted bits add up.
 
> The extra bits were hidden but parity was the price you paid for core 
> memory at the time
> for error checking.

Parity checking is the job of the memory controller, not the processor. In
fact, I am having a hard time thinking of a processor that did its own
parity checking in software (yes, I know any processor could do it, but
did any really do it?). Even if the parity checking is a lowly 74180, like
in a microcomputer - it is still not boggin down the processor. The
processor really doesn't need to know about parity, unless things go bad.
 
> I am not a IBM fan... I support 9 bit bytes. ( Bytes for a lack of 
> better name ).

9 is even more inefficient.

> The PDP-6/10's may of supported them but other than the CPU I am building
> I can't think of any other computer using them.

Some Univacs.

> To clairfy about IBM and bytes from a marketing standpoint it was a way to
> misslead the potential computer buyers from my veiw point that with the new
> marketing terms -- byte vs words , 32 vs 36 bits so that IBM's products 
> would
> look better compared to the 7 dwarfs at the time.

Going back a few days to a previous thread about books, I suggest you read
pages 148 and 149 of *IBMs System 360 and Early 370 Computers*. You may
then see that there was no conspiracy against sixbit.

William Donzelli
aw288 at osfn.org