4 May
2017
4 May
'17
12:53 p.m.
On 05/03/2017 05:37 PM, Systems Glitch wrote:
I want to say the only 12-bit work I've done has
always been octal
(PDP-8), but 8- and 16-bit has been a mix. I can switch between them,
but it's kinda like using vim and $graphical_work_editor -- you use
vim on a weekend long hack session and you keep hitting `ESC:wq` in
$graphical_work_editor!
Sometimes the choice of radix makes sense. At one point in my career, I
was reading both 60 bit octal dumps and 64 bit hex dumps. In both
cases, the radix made sense. The 60 bit words had a natural bit
grouping of 3 (6-bit characters, 6 bit opcode, 3 bit register numbers)
and the 64-bit one also was suited to hex (8 bit opocdes and register
numbers as well as characters). The only gotcha was that addresses were
bit addresses, so that calculating byte addresses with a byte index
involved a 3 bit shift and word addresses involved a 6 bit shift.
Halfwords involved a 5 bit shift, which didn't work for any common radix.
--Chuck