28 Feb
2002
28 Feb
'02
8:10 a.m.
Andreas Freiherr wrote:
Ben,
let me continue to be picky, as I often learn new things by trying to
really and thoroughly understand how something works. ;-)
This example was made as a general example not a real machine.
Will work for some, but not all, media. RL01/RL02, for
example, can be
done this way. I have seen a four-word bootstrap that indeed only
consists of putting the required command into the CSR and then WAITing.
Operating instructions: "let the program run for a few seconds, then
HALT and restart at address zero."
The front panel is your friend.:)
Will the IRQ really clear the halt F/F, causing the processor to resume
running? - I need to get my machines running soon, memory is fading...
While this was not a real example, often a bootstrap I suspect could use
of
tricks with the hardware after reset.
Other disk types, such as the RXs, require loading of
more than one
sector, and not many controllers are like the RK11 in that they
automatically increment sector counters.
But did not the big disc controllers have front panel as well?
I always used paper tape on a PDP-8 with a front panel.
What I wanted to point out is that you need to have
some kind of
"handler" for the reset button if you want your PDP-11 to have a life
after that. I might call this "handler" a "bootstrap" :-) - And I
intended to have a PDP-11 processor execute the instructions, not a
human! ;-)
One other factor with device drivers like on the PDP-8 they had to be
small and support swapping all of core to and from disk.
--
Andreas Freiherr
Vishay Semiconductor GmbH, Heilbronn, Germany
http://www.vishay.com
--
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html