2 Jun
2002
2 Jun
'02
9:35 a.m.
Cameron Kaiser wrote:
On the 6509, there are four extra address lines,
giving you up to 1MB.
These lines are set by location $0000 for execution (which 64K "bank" the
code is running from) and by location $0001 for indirection (i.e., on
indirect indexed LDAs and STAs *only* the four bits in $01 would be
asserted on the address lines to get at another bank). Not quite segment
and offset addressing. :-)
And the 8086 segment addressing is a improvement?
The only clean 8 bit extended addressing was with the 6809 and OS/9
level Two.
Here you had 16 pages ( 4kb-each ) of virtual memory ,if I remember
right, per
processes with the upper 256 bytes common memory.
--
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html