28 Jun
2013
28 Jun
'13
9:31 a.m.
On Jun 28, 2013, at 9:21 AM, ben <bfranchuk at jetnet.ab.ca> wrote:
The point I was making was that 9 bit bytes are a better word size for bytes. The PDP 11
went 8 bits and that we know in hindsight is just too small.
In the PDP-10 instruction set, you get to pick the size of the bytes. It's a word
addressed machine (36-bit words). If you want "bytes" you use the "byte
pointer" instructions. In those instructions you specify the size of a
"byte". It can be anywhere from 1 to 35 bits. So there's nothing
"special" about 9-bits (other than it divides into 36 evenly...but then so does
18, 6, 3, 2 and 1). But the byte pointer instructions don't care if a word can't
hold an integral number of "bytes". The left-over bits aren't used.
TTFN - Guy