Byte sizes (was Re: 2.8M 3.5' floppy

woodelf bfranchuk at jetnet.ab.ca
Mon Mar 14 22:45:38 CST 2005


William Donzelli wrote:

>>Umm 6 bits is perfect for BCD, look at IBM's 1620 : 4 bits BCD, 1 bit 
>>sign flag/length flag 1 bit parity
>>    
>>
>
>Very inefficient. I hope you are not serious.
>
>Back in the 1960s, most data was numeric, due to banking. It may still be
>the dominant form (with maybe porn mpgs a close second).
>
Lets call this multi-media to include music downloads. If I want porn 
rather get a DVD
than a mpg. :)

> Each field of a
>database might have 10, 12, perhaps 16 BCD characters. Why on Earth would
>you want a sign bit associated with each one? If the field even needed a
>sign, only one would be needed. Parity? That is the job of the memory
>controller - having the processor figure out parity is just a waste of
>CPU.
>  
>
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.

>You need to realize that back in the 1960, each bit was counted with a
>price tag. A medium sized mainframe might only have 64K with a few tens of
>megs on disk. A batch might take all night to run, with no time for
>fooling around with extra bits.
>
>  
>
The extra bits were hidden but parity was the price you paid for core 
memory at the time
for error checking.

>Basically, sixbit died when it should have. The DEC 36 bit line suffered
>from really bad timing (the S/360 was being planned, unknown to DEC, when
>the PDP-6 was being wheeled out. The S/360 made the world 8 bits, and
>signed the PDP-6/10s death certificate.).
>
>  
>
I am not a IBM fan... I support 9 bit bytes. ( Bytes for a lack of 
better name ).
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.
(Well I got some of the hardware already ... 1'st build the case to hold
the front panel)
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. Just like stating raw 
clock speed
today for marketing. I can buy a N GHZ machine but can anybody tell me 
the real
speed of instruction abc on data xyz?
Ben alias woodelf







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