26 Oct
2010
26 Oct
'10
5:40 p.m.
On 26 Oct 2010 at 17:13, Eric Smith wrote:
The 8080 instruction encoding is based on 3 bit fields
for register
selection, so octal is natural. Split octal for 16-bit addresses
resulted from the way 16-bit addresses were stored in memory as two
consecutive bytes. If a JMP instruction was stored in memory in octal
as 303 222 111, it was more natural to consider the address to be 111
222 in split octal rather than 044622 in 16-bit octal.
When I wrote a cross-assembler for the 8008, I used octal. When I
went to the 8080, I used hex. The only difference was the projects I
worked with at the day job--one mainframe used octal; the other used
hex. Both from the same manufacturer.
I liked the IMSAI scheme of color-coding the front panel toggles, so
you could group them by 3 or 4 as your preference demanded.
I found that octal on the PDP-11 with 16-bit words and 8 bit bytes
was unnecessarily confusing.
The GI CP1600 16-bit micro also used octal. A waste of ink.
So, what's best (octal or hex) for a system with 33 bit words and 11
bit characters?
--Chuck