28 Sep
2004
28 Sep
'04
3:02 p.m.
Andy Holt wrote:
On the CDC6600 - and, for that matter most machine architectures that
preceded the IBM /360 - the subroutine call instruction writes a jump to the
return address as the first word of the subroutine and then branches to the
second. Before Manchester invented "B-lines" (index registers)
self-modifying code was needed even for indexing.
What about later machines like the PDP-8, that I have used.
The next machine I build I don't plan to have index registers
just simple indirect addressing. I have done one or two designs
in a FPGA but this time I want to use real TTL.
Anybody got a good web link on decimal floating point,I am not sure
how to handle the sign bit with decimal math for adc operations.
It is almost a definition of a modern architecture
that code need not be
(and often cannot be) self-modifying.
ROM able code does say a lot about how you
program your machine.
Andy
Ben.